Resist composition and method of forming resist pattern

ABSTRACT

A resist composition including a resin component whose solubility in a developing solution is changed due to an action of an acid, in which the resin composition has a constitutional unit derived from a compound containing a chain-like aliphatic acid dissociable group or a monocyclic aliphatic acid dissociable group and a constitutional unit derived from a compound containing an aromatic hydrocarbon group-containing acid dissociable group.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a resist composition and a method offorming a resist pattern.

Priority is claimed on Japanese Patent Application No. 2017-248498,filed on Dec. 25, 2017, the content of which is incorporated herein byreference.

Description of Related Art

In lithography techniques, for example, a resist film formed of a resistmaterial is formed on a substrate, and the resist film is subjected toselective exposure, followed by a development treatment, thereby forminga resist pattern having a predetermined shape on the resist film. Aresist material in which the exposed portions of the resist film becomesoluble in a developing solution is called a positive type, and a resistmaterial in which the exposed portions of the resist film becomeinsoluble in a developing solution is called a negative type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have led torapid progress in the field of pattern miniaturization. Typically, theseminiaturization techniques involve shortening the wavelength (increasingthe energy) of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are used in massproduction. Furthermore, research is also being conducted intolithography techniques that use an exposure light source having awavelength shorter (energy higher) than these excimer lasers, such aselectron beams (EB), extreme ultraviolet radiation (EUV), and X rays.

Resist materials for use with these types of exposure light sourcesrequire lithography characteristics such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these requirements, in the relatedart, a chemically amplified composition which includes a base materialcomponent whose solubility in a developing solution is changed due to anaction of an acid and an acid-generator component that generates an acidupon exposure has been used.

For example, in a case where the developing solution is an alkalideveloping solution (alkali developing process), as a positive typechemically amplified resist, a composition which contains a basematerial component (base resin) whose solubility in an alkali developingsolution is increased due to an action of an acid and an acid generatorcomponent has been typically used. In a case where a resist film formedusing such a resist composition is selectively exposed at the time offorming a resist pattern, in exposed portions, an acid is generated fromthe acid generator component, and the polarity of the base resinincreases by the action of the generated acid, thereby making theexposed portions of the resist film soluble in the alkali developingsolution. Thus, by conducting alkali development, the exposed portionsof the resist film are dissolved and removed, and the unexposed portionsof the resist film remain to form a positive type resist pattern (forexample, see Japanese Unexamined Patent Application, First PublicationNo. 2003-241385).

On the other hand, in a case where such a base resin is applied to asolvent developing process using a developing solution containing anorganic solvent (organic developing solution), the solubility of theexposed portions in an organic developing solution is decreased. As aresult, the unexposed portions of the resist film are dissolved andremoved by the organic developing solution, and a negative type resistpattern in which the exposed portions of the resist film are remainingis formed. Such a solvent developing process for forming a negative typeresist composition is also referred to as “negative type developingprocess” (for example, see Japanese Unexamined Patent Application, FirstPublication No. 2007-084502).

In recent years, with the progress of miniaturization of a resistpattern, for example, in lithography using electron beams or EUV,formation of fine patterns having a size of several tens of nanometershas been targeted (J. Vac. Sci. Technol. B24 (2006) 3055). As the sizeof a resist pattern decreases as described above, a resist compositionis required to have high resolution performance.

Moreover, since there is a problem in that outgas generated by theprogress of a deprotection reaction of a protective group contained in aresin contaminates an exposure device, the solution has been sought.

In addition, with the progress of miniaturization of patterns, a resistfilm to be formed has been thinned. For example, in a case of EB or EUVapplications, a film thickness of 60 nm or less has been examined (Proc.of SPIE Vol. 7271 727124 (2009)). In such a situation, it is importantto suppress a decrease in film thickness of a resist film at the time ofperforming exposure and development on a resist film. For example, in acase of a positive type pattern, unexposed portions remain without beingremoved at the time of development, but there is a concern thatunevenness occurs on the upper surface of the resist pattern due to thedecrease in film thickness and the resolution or pattern shapedeteriorates.

For example, Japanese Unexamined Patent Application, First PublicationNo. 2011-123463 describes a polymer compound that has a constitutionalunit having a naphthalene ring at the terminal of a side chain, as abase material component of a resist composition which has excellentlithographic characteristics and in which a decrease in film thicknessduring the formation of a resist pattern is suppressed.

SUMMARY OF THE INVENTION

With further progress of lithography techniques and further promotion ofminiaturization of a resist pattern, there has been a growing demand fora resist material to form a resist pattern with higher resolution whilemaintaining excellent lithography characteristics.

The present invention has been made in consideration of theabove-described problems, and an object thereof is to provide a resistcomposition in which various lithography characteristics are favorablybalanced and the resolution and roughness are improved; and a method offorming a resist pattern obtained by using the resist composition.

In order to solve the above-described problems, the present inventionemploys the following configurations.

In other words, according to a first aspect of the present invention,there is provided a resist composition which generates an acid uponexposure and whose solubility in a developing solution is changed due toan action of the acid, the composition including: a resin component (A1)whose solubility in a developing solution is changed due to the actionof the acid, in which the resin component (A1) has a constitutional unit(a0-1) derived from a compound represented by Formula (a0-1) and aconstitutional unit (a0-2) derived from a compound represented byFormula (a0-2).

[In the formula, W represents a polymerizable group-containing group,and Ra⁰¹ represents an acid dissociable group represented by Formula(a01-r-1) or (a01-r-2).]

[In the formulae, Ra⁰¹¹ to Ra⁰¹³ each independently represent a linearor branched aliphatic hydrocarbon group, Ra⁰¹⁴ represents a linear orbranched aliphatic hydrocarbon group, Ra⁰¹⁵ represents a group thatforms a monocyclic aliphatic cyclic group together with a carbon atom towhich Ra⁰¹⁴ is bonded, and the symbol “*” represents a bonding site.]

[In the formula, W represents a polymerizable group-containing group,and Ra⁰² represents an acid dissociable group represented by Formula(a02-r-1).]

[In the formula, Ra⁰²¹ and Ra⁰²² each independently represent a linearor branched aliphatic hydrocarbon group, Ra⁰²³ represents an aromatichydrocarbon group, and the symbol “*” represents a bonding site]

According to a second aspect of the present invention, there is provideda method of forming a resist pattern, including: a step of forming aresist film on a support using the resist composition according to thefirst aspect; a step of exposing the resist film; and a step ofdeveloping the exposed resist film to form a resist pattern.

According to the present invention, it is possible to provide a resistcomposition in which various lithography characteristics are favorablybalanced and the resolution and roughness are improved; and a method offorming a resist pattern obtained by using the resist composition.

DETAILED DESCRIPTION OF THE INVENTION

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon, unless otherwise specified. The same applies forthe alkyl group in an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic, divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which some or all hydrogenatoms of an alkyl group is substituted with halogen atoms. Examples ofthe halogen atom include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a groupin which some or all hydrogen atoms of an alkyl group or an alkylenegroup have been substituted with fluorine atoms.

The term “constitutional unit” indicates a monomer unit that contributesto the formation of a polymeric compound (a resin, a polymer, or acopolymer).

The expression “may have a substituent” means that a case where ahydrogen atom (—H) is substituted with a monovalent group, or a casewhere a methylene (—CH₂—) group is substituted with a divalent group.

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

A “constitutional unit derived from acrylic acid ester” indicates aconstitutional unit that is formed by the cleavage of the ethylenicdouble bond of acrylic acid ester.

The “acrylic acid ester” indicates a compound in which the terminalhydrogen atom of the carboxy group of acrylic acid (CH₂═CH—COOH) hasbeen substituted with an organic group.

The acrylic acid ester may have the hydrogen atom bonded to the carbonatom at the α-position substituted with a substituent. The substituent(R^(α0)) that substitutes the hydrogen atom bonded to the carbon atom atthe α-position is an atom other than hydrogen or a group, and examplesthereof include an alkyl group having 1 to 5 carbon atoms and ahalogenated alkyl group having 1 to 5 carbon atoms. Further, acrylicacid ester having the hydrogen atom bonded to the carbon atom at theα-position substituted with a substituent (R^(α0)) in which thesubstituent has been substituted with a substituent containing an esterbond (itaconic acid diester), or an acrylic acid having the hydrogenatom bonded to the carbon atom at the α-position substituted with asubstituent (R^(α0)) in which the substituent has been substituted witha hydroxyalkyl group or a group in which the hydroxyl group in ahydroxyalkyl group has been modified (α-hydroxyalkyl acrylic acid ester)can be exemplified as acrylic acid ester having the hydrogen atom bondedto the carbon atom at the α-position substituted with a substituent. Acarbon atom at the α-position of acrylic acid ester indicates the carbonatom bonded to the carbonyl group, unless specified otherwise.

Hereinafter, acrylic acid ester in which the hydrogen atom bonded to thecarbon atom at the α-position is substituted with a substituent is alsoreferred to as α-substituted acrylic acid ester”. Further, acrylic acidester and α-substituted acrylic acid ester are also collectivelyreferred to as “(α-substituted) acrylic acid ester”. Further, an acrylicacid in which a hydrogen atom bonded to the carbon atom at theα-position is substituted with a substituent is also referred to asα-substituted acrylic acid. In addition, acrylic acid and α-substitutedacrylic acid are also collectively referred to as “(α-substituted)acrylic acid”.

A “constitutional unit derived from acrylamide” indicates aconstitutional unit that is formed by the cleavage of the ethylenicdouble bond of acrylamide.

The acrylamide may have the hydrogen atom bonded to the carbon atom atthe α-position substituted with a substituent, and may have either orboth terminal hydrogen atoms on the amino group of acrylamidesubstituted with a substituent. A carbon atom at the α-position of anacrylamide indicates the carbon atom bonded to the carbonyl group,unless specified otherwise.

As the substituent which substitutes the hydrogen atom bonded to thecarbon atom at the α-position of acrylamide, the same substituents asthose described above for the substituent (R^(α0)) at the α-position ofthe above-described α-position of the above-described α-substitutedacrylic acid ester can be exemplified.

A “constitutional unit derived from hydroxystyrene” indicates aconstitutional unit that is formed by the cleavage of an ethylenicdouble bond of hydroxystyrene. A “constitutional unit derived from ahydroxystyrene derivative” indicates a constitutional unit formed by thecleavage of an ethylenic double bond of a hydroxystyrene derivative.

The term “hydroxystyrene derivative” includes compounds in which thehydrogen atom at the α-position of hydroxystyrene has been substitutedwith another substituent such as an alkyl group or a halogenated alkylgroup; and derivatives thereof. Examples of the derivatives thereofinclude hydroxystyrene in which the hydrogen atom of the hydroxyl grouphas been substituted with an organic group and may have the hydrogenatom at the α-position substituted with a substituent; andhydroxystyrene which has a substituent other than a hydroxyl groupbonded to the benzene ring and may have the hydrogen atom at theα-position substituted with a substituent. Here, the α-position (carbonatom at the α-position) indicates the carbon atom having the benzenering bonded thereto, unless specified otherwise.

As the substituent which substitutes the hydrogen atom at the α-positionof hydroxystyrene, the same substituents as those described above forthe substituent at the α-position of the above-described α-substitutedacrylic acid ester can be exemplified.

A “constitutional unit derived from vinylbenzoic acid or a vinylbenzoicacid derivative” indicates a constitutional unit that is formed by thecleavage of the ethylenic double bond of vinylbenzoic acid or avinylbenzoic acid derivative.

The term “vinylbenzoic acid derivative” includes compounds in which thehydrogen atom at the α-position of vinylbenzoic acid has beensubstituted with another substituent such as an alkyl group or ahalogenated alkyl group; and derivatives thereof. Examples of thederivatives thereof include vinylbenzoic acid in which the hydrogen atomof the carboxy group has been substituted with an organic group and mayhave the hydrogen atom at the α-position substituted with a substituent;and vinylbenzoic acid which has a substituent other than a hydroxylgroup and a carboxy group bonded to the benzene ring and may have thehydrogen atom at the α-position substituted with a substituent. Here,the α-position (carbon atom at the α-position) indicates the carbon atomhaving the benzene ring bonded thereto, unless specified otherwise.

As the alkyl group as a substituent at the α-position, a linear orbranched alkyl group is preferable, and specific examples thereofinclude alkyl groups of 1 to 5 carbon atoms, such as a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group.

Specific examples of the halogenated alkyl group as the substituent atthe α-position include groups in which some or all hydrogen atoms of theabove-described “alkyl group as the substituent at the α-position” aresubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly preferable.

Specific examples of the hydroxyalkyl group as the substituent at theα-position include groups in which some or all hydrogen atoms of theabove-described “alkyl group as the substituent at the α-position” aresubstituted with a hydroxyl group. The number of hydroxyl groups in thehydroxyalkyl group is preferably 1 to 5, and most preferably 1.

In the present specification and the scope of the present patent claims,asymmetric carbons may be present or enantiomers or diastereomers may bepresent depending on the structures of the chemical formulae. In thiscase, these isomers are represented by one formula. These isomers may beused alone or in the form of a mixture.

(Resist Composition)

The resist composition according to the present embodiment is a resistcomposition which generates an acid upon exposure and whose solubilityin a developing solution is changed due to an action of the acid.

Such a resist composition contains a base material component (A) inwhich the solubility in a developing solution is changed due to anaction of the acid (hereinafter, also referred to as “component (A)”).

In a case where a resist film is formed using the resist compositionaccording to the present embodiment and the formed resist film issubjected to a selective exposure, acid is generated at exposed portionsof the resist film, and the generated acid acts on the component (A) tochange the solubility of the component (A) in a developing solution,whereas the solubility of the component (A) in a developing solution isnot changed at unexposed portions of the resist film, thereby generatingdifference in solubility in a developing solution between exposedportions and unexposed portions of the resist film. Therefore, bysubjecting the resist film to development, the exposed portions of theresist film are dissolved and removed to form a positive type resistpattern in a case of a positive type resist, whereas the unexposedportions of the resist film are dissolved and removed to form a negativetype resist pattern in a case of a negative type resist.

In the present specification, a resist composition which forms apositive type resist pattern by dissolving and removing the exposedportions of the resist film is called a positive type resistcomposition, and a resist composition which forms a negative type resistpattern by dissolving and removing the unexposed portions of the resistfilm is called a negative type resist composition.

The resist composition of the present embodiment may be a positive typeresist composition or a negative type resist composition.

Further, in the formation of a resist pattern, the resist composition ofthe present embodiment can be applied to an alkali developing processusing an alkali developing solution in the developing treatment, or asolvent developing process using a developing solution containing anorganic solvent (organic developing solution) in the developingtreatment.

In other words, the resist composition of the present embodiment is a“positive type resist composition for an alkali developing process” thatforms a positive type resist pattern in an alkali developing process andis a “negative type resist composition for a solvent developing process”that forms a negative type resist pattern in a solvent developingprocess.

The resist composition of the present embodiment has a function ofgenerating acid upon exposure, and in the resist composition, thecomponent (A) may generate an acid upon exposure, or an additivecomponent other than the component (A) may generate an acid uponexposure.

In the present embodiment, the resist composition may be a resistcomposition (1) containing an acid generator component (B) whichgenerates acid upon exposure (hereinafter, referred to as “component(B)”); a resist composition (2) in which the component (A) is acomponent which generates acid upon exposure; or a resist composition(3) in which the component (A) is a component which generates acid uponexposure, and further containing an acid generator component (B).

That is, in a case where the resist composition of the present inventionis the above-described resist composition (2) or (3), the component (A)is a “base material component which generates acid upon exposure andwhose solubility in a developing solution is changed due to an action ofan acid”. In a case where the component (A) is a base material componentwhich generates an acid upon exposure and whose solubility in adeveloping solution is changed due to an action of an acid, thecomponent (A1) described below is preferably a polymeric compound whichgenerates an acid upon exposure and whose solubility in a developingsolution is changed due to an action of an acid. As the polymericcompound, a copolymer having a constitutional unit which generates acidupon exposure can be used.

As the constitutional unit which generates acid upon exposure, a knownconstitutional unit can be used.

It is particularly preferable that the resist composition of the presentembodiment corresponds to the case of (1) described above.

<Component (A)>

The component (A) is a base material component whose solubility in adeveloping solution is changed due to an action of an acid.

In the present invention, the term “base material component” indicatesan organic compound capable of forming a film, and is preferably anorganic compound having a molecular weight of 500 or greater. In a casewhere the organic compound has a molecular weight of 500 or greater, thefilm-forming ability is improved, and a resist pattern at a nano levelcan be easily formed.

The organic compound used as the base material component is broadlyclassified into non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereinafter, a “lowmolecular weight compound” indicates a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 orgreater is generally used. Hereinafter, a “resin” or a “polymericcompound” indicates a polymer having a molecular weight of 1,000 orgreater.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

The component (A) in the resist composition of the present embodimentcontains a resin component (A1) (hereinafter, also referred to as a“component (A1)”) in which the solubility in a developing solution ischanged due to an action of an acid.

As the component (A), at least the component (A1) is used, and otherpolymer compounds and/or low molecular weight compounds may be used incombination with the component (A1).

<<Component (A1)>>

The component (A1) contains a constitutional unit (a0-1) derived from acompound represented by Formula (a0-1) and a constitutional unit (a0-2)derived from a compound represented by Formula (a0-2). Such a component(A1) may contain other constitutional units as necessary in addition tothe constitutional unit (a0-1) and the constitutional unit (a0-2).

In the resist composition of the present embodiment, since theconstitutional unit (a0-1) and the constitutional unit (a0-2) contain anacid dissociable group, the polarity of the resin component is changedbefore and after the exposure by using the (A1) component. In the alkalideveloping process and the solvent developing process, an excellentdevelopment contrast between exposed portions and unexposed portions ofthe resist film can be obtained.

In a case of applying an alkali developing process, the component (A1)is substantially insoluble in an alkali developing solution prior toexposure, but in a case where acid is generated from the component (B)upon exposure, the action of this acid causes an increase in thepolarity of the base material component, thereby increasing thesolubility of the component (A1) in an alkali developing solution.Therefore, in the formation of a resist pattern, by conducting selectiveexposure of a resist film formed by applying the resist composition to asubstrate, the exposed portions of the resist film change from aninsoluble state to a soluble state in an alkali developing solution,whereas the unexposed portions of the resist film remain insoluble in analkali developing solution, and hence, a positive type resist pattern isformed by alkali developing.

Meanwhile, in a case of a solvent developing process, the component (A1)exhibits high solubility in an organic developing solution prior toexposure, and in a case where acid is generated from the component (B)upon exposure, the polarity of the component (A1) is increased by theaction of the generated acid, thereby decreasing the solubility of thecomponent (A1) in an organic developing solution. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by applying the resist composition to a substrate,the exposed portions of the resist film changes from an soluble state toan insoluble state in an organic developing solution, whereas theunexposed portions of the resist film remain soluble in an organicdeveloping solution. As a result, by conducting development using anorganic developing solution, a negative type resist pattern can beformed.

In regard to constitutional unit (a0-1):

The constitutional unit (a0-1) is a constitutional unit derived from acompound (hereinafter, also referred to as a “compound (a0)”)represented by Formula (a0-1).

[In the formula, W represents a polymerizable group-containing group.Ra⁰¹ represents an acid dissociable group represented by Formula(a01-r-1) or (a01-r-2).]

[In the formulae, Ra⁰¹¹ to Ra⁰¹³ each independently represent a linearor branched aliphatic hydrocarbon group. Ra⁰¹⁴ represents a linear orbranched aliphatic hydrocarbon group. Ra⁰¹⁵ represents a group thatforms a monocyclic aliphatic cyclic group together with the carbon atomto which Ra⁰¹⁴ is bonded. The symbol “*” represents a bonding site.]

In Formula (a0-1), W represents a polymerizable group-containing group.

The “polymerizable group” as W indicates a group that enablespolymerization of a compound containing a polymerizable group throughradical polymerization or the like and has a multiple bond betweencarbon atoms, such as an ethylenic double bond.

Examples of the polymerizable group include a vinyl group, an allylgroup, an acryloyl group, a methacryloyl group, a fluorovinyl group, adifluorovinyl group, a trifluorovinyl group, a difluorotrifluoromethylvinyl group, a trifluoroallyl group, a perfluoroallyl group, atrifluoromethyl acryloyl group, a nonylfluorobutyl acryloyl group, avinyl ether group, a fluorine-containing vinyl ether group, an allylether group, a fluorine-containing allyl ether group, a styryl group, avinyl naphthyl group, a fluorine-containing styryl group, afluorine-containing vinyl naphthyl group, a norbornyl group, afluorine-containing norbornyl group, and a silyl group.

As the polymerizable group-containing group, a group formed of only apolymerizable group or a group formed of a polymerizable group and agroup other than the polymerizable group may be employed. Examples ofthe group other than the polymerizable group include a divalenthydrocarbon group which may have a substituent and a divalent linkinggroup having hetero atoms.

As W, a group represented by Chemical Formula: CH₂═C(R)—Ya^(x0)- issuitably exemplified. In this chemical formula, R represents a hydrogenatom, an alkyl group having 1 to 5 carbon atoms, or a halogenated alkylgroup having 1 to 5 carbon atoms, and Ya^(x0) represents a single bondor a divalent linking group.

In the chemical formula shown above, as the alkyl group having 1 to 5carbon atoms as R, a linear or branched alkyl group having 1 to 5 carbonatoms is preferable, and specific examples thereof include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, and a neopentyl group. The halogenated alkyl grouphaving 1 to 5 carbon atoms is a group in which some or all hydrogenatoms of the above-described alkyl group having 1 to 5 carbon atoms havebeen substituted with halogen atoms. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom, and a fluorine atom is particularly preferable. As R, a hydrogenatom, an alkyl group having 1 to 5 carbon atoms, or a fluorinated alkylgroup having 1 to 5 carbon atoms is preferable, a hydrogen atom or amethyl group is more preferable, and a methyl group is particularlypreferable in terms of industrial availability.

In the chemical formula shown above, the divalent linking group asYa^(x0) is not particularly limited, and suitable examples thereofinclude a divalent hydrocarbon group which may have a substituent and adivalent linking group having hetero atoms.

Divalent Hydrocarbon Group which May have Substituent:

In a case where Ya^(x0) represents a divalent hydrocarbon group whichmay have a substituent, the hydrocarbon group may be an aliphatichydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group as Ya^(x0)

The aliphatic hydrocarbon group indicates a hydrocarbon group that hasno aromaticity. The aliphatic hydrocarbon group may be saturated orunsaturated. In general, the aliphatic hydrocarbon group is preferablysaturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group has preferably 1 to 10 carbonatoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4carbon atoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group has preferably 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, a branched alkylene groupis preferred, and specific examples thereof include alkylalkylenegroups, for example, alkylmethylene groups such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—;and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in the alkylalkylene group, alinear alkyl group having 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group having 1 to 5 carbon atoms which has beensubstituted with a fluorine atom, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing Ring in Structure Thereof

Examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof include a cyclic aliphatic hydrocarbon group which mayhave a substituent containing a hetero atom in the ring structurethereof (a group in which two hydrogen atoms have been removed from analiphatic hydrocarbon ring), a group in which the cyclic aliphatichydrocarbon group is bonded to the terminal of a linear or branchedaliphatic hydrocarbon group, and a group in which the cyclic aliphatichydrocarbon group is interposed in a linear or branched aliphatichydrocarbon group. As the linear or branched aliphatic hydrocarbongroup, the same groups as those described above can be used.

The cyclic aliphatic hydrocarbon group has preferably 3 to 20 carbonatoms and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which two hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane has preferably 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic alicyclic hydrocarbon group, a group in which two hydrogenatoms have been removed from a polycycloalkane is preferable. As thepolycycloalkane, a group having 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group,an n-butyl group, or a tert-butyl group is particularly preferable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an iso-propoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atomis preferable.

Examples of the halogenated alkyl group as the substituent includegroups in which some or all hydrogen atoms in the above-described alkylgroups have been substituted with the above-described halogen atoms.

In the cyclic aliphatic hydrocarbon group, some carbon atomsconstituting the ring structure thereof may be substituted with asubstituent containing a hetero atom. As the substituent containing ahetero atom, —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group as Ya^(x0)

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclicconjugated system having (4n+2) π electrons, and may be monocyclic orpolycyclic. The aromatic ring has preferably 5 to 30 carbon atoms, morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 12 carbon atoms. Here, the number ofcarbon atoms in a substituent is not included in the number of carbonatoms.

Examples of the aromatic ring include aromatic hydrocarbon rings such asbenzene, naphthalene, anthracene, and phenanthrene; and aromatic heterorings in which some carbon atoms constituting the above-describedaromatic hydrocarbon rings have been substituted with hetero atoms.Examples of the hetero atom in the aromatic hetero rings include anoxygen atom, a sulfur atom, and a nitrogen atom. Specific examples ofthe aromatic hetero ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the above-describedaromatic hydrocarbon ring or aromatic hetero ring (an arylene group or aheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof a group (an aryl group or a heteroaryl group) obtained by removingone hydrogen atom from the above-described aromatic hydrocarbon ring oraromatic hetero ring has been substituted with an alkylene group (agroup in which one hydrogen atom has been further removed from the arylgroup in the above-described arylalkyl group such as a benzyl group, aphenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene groupwhich is bonded to the above-described aryl group or heteroaryl grouphas preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms,and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom in thearomatic hydrocarbon group may be substituted with a substituent. Forexample, the hydrogen atom bonded to the aromatic ring in the aromatichydrocarbon group may be substituted with a substituent. Examples ofsubstituents include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group,an n-butyl group, or a tert-butyl group is more preferable.

As the alkoxy group, the halogen atom, and the halogenated alkyl groupas the substituents, the same groups as the above-described substituentgroups for substituting a hydrogen atom in the cyclic aliphatichydrocarbon group can be exemplified.

Divalent Linking Group Containing Hetero Atom:

In a case where Ya^(x0) represents a divalent linking group containing ahetero atom, preferred examples of the linking group include —O—,—C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (H may be substituted with a substituent such as an alkylgroup, an acyl group, or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by Formula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—,—C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or—Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²² each independentlyrepresent a divalent hydrocarbon group which may have a substituent, 0represents an oxygen atom, and m″ represents an integer of 0 to 3].

In a case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH— or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group, or the like.The substituent (an alkyl group, an acyl group, or the like) haspreferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms,and most preferably 1 to 5 carbon atoms.

In Formulae —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represent a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe above-described divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, a linearalkylene group is more preferable, a linear alkylene group having 1 to 5carbon atoms is still more preferable, and a methylene group or anethylene group is particularly preferable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group, or an alkylmethylene group ismore preferable. The alkyl group in the alkylmethylene group ispreferably a linear alkyl group having 1 to 5 carbon atoms, morepreferably a linear alkyl group having 1 to 3 carbon atoms, and mostpreferably a methyl group.

In the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and particularly preferably 1. In other words, it isparticularly preferable that the group represented by Formula—[Y²¹—C(═O)—O]_(m″)—Y²²— is a group represented by Formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by Formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′represents an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1. b′ represents an integer of 1 to 10, preferably an integerof 1 to 8, more preferably an integer of 1 to 5, still more preferably 1or 2, and most preferably 1.

In the description above, as Ya^(x0), a single bond, an ester bond[—C(═O)—O— or —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of these is preferable, a single bondor an ester bond [—C(═O)—O— or —O—C(═O)—] is more preferable, and anester bond [—C(═O)—O—] is particularly preferable.

In Formula (a0-1), Ra⁰¹ represents an acid dissociable group representedby Formula (a01-r-1) or (a01-r-2).

In Formula (a01-r-1), Ra⁰¹¹ to Ra⁰¹³ each independently represent alinear or branched aliphatic hydrocarbon group.

As the linear aliphatic hydrocarbon group, a linear alkyl group having 1to 5 carbon atoms or a linear alkenyl group having 2 to 5 carbon atomsis preferable.

Examples of the linear alkyl group having 1 to 5 carbon atoms include amethyl group, an ethyl group, a propyl group, an n-butyl group, and apentyl group.

Examples of the alkenyl group having 2 to 5 carbon atoms include a vinylgroup, a propenyl group (allyl group), and a butynyl group.

As the branched aliphatic hydrocarbon group, a linear alkyl group having3 to 5 carbon atoms or a branched alkenyl group having 3 to 5 carbonatoms is preferable. Examples of the linear alkyl group having 3 to 5carbon atoms include an isopropyl group, an isobutyl group, a tert-butylgroup, an isopentyl group, and a neopentyl group.

Examples of the branched alkenyl group having 3 to 5 carbon atomsinclude a 1-methylvinyl group, a 2-methylvinyl group, a 1-methylpropenylgroup, and a 2-methylpropenyl group.

Ra⁰¹¹ to Ra⁰¹³ represent preferably a linear alkyl group having 1 to 5carbon atoms or a linear alkenyl group having 2 to 5 carbon atoms andmore preferably a methyl group, an ethyl group, or an isopropyl group.

Specific examples of the acid dissociable group represented by Formula(a01-r-1) include the followings. The symbol “*” represents a bondingsite.

In Formula (a01-r-2), Ra⁰¹⁴ represents a linear or branched aliphatichydrocarbon group.

Examples of the linear or branched aliphatic hydrocarbon group as Ra⁰¹⁴include those exemplified as the linear or branched aliphatichydrocarbon groups represented by Ra⁰¹¹ to Ra⁰¹³.

Among these, as Ra⁰¹⁴, a linear alkyl group having 1 to 5 carbon atomsor a linear alkenyl group having 2 to 5 carbon atoms is preferable, anda methyl group, an ethyl group, an isopropyl group, or a vinyl group ismore preferable.

In Formula (a01-r-2), Ra⁰¹⁵ represents a group that forms a monocyclicaliphatic cyclic group together with the carbon atom to which Ra⁰¹⁴ isbonded. As the monocyclic aliphatic cyclic group, a group in which onehydrogen atom is removed from a monocycloalkane is preferable. Thenumber of carbon atoms of the monocycloalkane is preferably in a rangeof 3 to 6, and specific examples thereof include cyclopentane,cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane,cycloundecane, and cyclododecane.

Among these, cyclopentane or cyclohexane is preferable as the monocyclicaliphatic cyclic group that is formed by Ra⁰¹⁵ together with the carbonatom to which Ra⁰¹⁴ is bonded.

Specific examples of the acid dissociable group represented by Formula(a01-r-2) are shown below. The symbol “*” represents a bonding site.

As the constitutional unit (a0-1), a constitutional unit represented byFormula (a0-1-1) is preferable.

[In the formula, R represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms. Va⁰¹ represents a divalent hydrocarbon group which may have anether bond, and n_(a01) represents 0 to 2. Ra⁰¹¹ represents an aciddissociable group represented by Formula (a01-r-11) or (a01-r-21).]

[In the formulae, Ra⁰¹¹′ to Ra⁰¹³′ each independently represent a methylgroup, an ethyl group, or an isopropyl group. Ra⁰¹⁴′ represents a methylgroup, an ethyl group, an isopropyl group, or a vinyl group. Ra⁰¹⁵′represents a group that forms a cyclopentyl group or a cyclohexyl grouptogether with the carbon atom to which Ra⁰¹⁴′ is bonded.]

In Formula (a0-1-1), as the alkyl group having 1 to 5 carbon atoms as R,a linear or branched alkyl group having 1 to 5 carbon atoms ispreferable, and specific examples thereof include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl group,and a neopentyl group. The halogenated alkyl group having 1 to 5 carbonatoms is a group in which some or all hydrogen atoms of theabove-described alkyl group having 1 to 5 carbon atoms have beensubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom, and an iodine atom, anda fluorine atom is particularly preferable. As R, a hydrogen atom, analkyl group having 1 to 5 carbon atoms, or a fluorinated alkyl grouphaving 1 to 5 carbon atoms is preferable, a hydrogen atom or a methylgroup is more preferable, and a methyl group is particularly preferablein terms of industrial availability.

In Formula (a0-1-1), Va⁰¹ represents a divalent hydrocarbon group whichmay have an ether bond. The divalent hydrocarbon group as Va⁰¹ may be analiphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon grouprepresented by Va01 may be saturated or unsaturated, but it ispreferable that the aliphatic hydrocarbon group is saturated.

More specific examples of the aliphatic hydrocarbon group include alinear or branched aliphatic hydrocarbon group and an aliphatichydrocarbon group having a ring in the structure thereof.

The linear aliphatic hydrocarbon group has preferably 1 to 10 carbonatoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4carbon atoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group has preferably 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples thereof include alkylalkylenegroups, for example, alkylmethylene groups such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—;and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in the alkylalkylene group, alinear alkyl group having 1 to 5 carbon atoms is preferable.

Examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof include an alicyclic hydrocarbon group (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the alicyclic hydrocarbon group is bonded to theterminal of the above-described linear or branched aliphatic hydrocarbongroup, and a group in which the alicyclic hydrocarbon group isinterposed in the above-described linear or branched aliphatichydrocarbon group. The linear or branched aliphatic hydrocarbon group isthe same as defined for the above-described linear aliphatic hydrocarbongroup or the above-described branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group has preferably 3 to 20 carbon atoms andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a monocyclic group or apolycyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which two hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane has preferably 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic alicyclic hydrocarbon group, a group in which two hydrogenatoms have been removed from a polycycloalkane is preferable. As thepolycycloalkane, a group having 7 to 12 carbon atoms is preferable.Specific examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon grouprepresented by Va⁰¹ is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group has preferably 3 to 30 carbon atoms, morepreferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbonatoms, particularly preferably 6 to 15 carbon atoms, and most preferably6 to 10 carbon atoms. Here, the number of carbon atoms in a substituentis not included in the number of carbon atoms.

Specific examples of the aromatic ring contained in the aromatichydrocarbon group include aromatic hydrocarbon rings such as benzene,biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; andaromatic hetero rings in which some carbon atoms constituting theabove-described aromatic hydrocarbon rings have been substituted withhetero atoms. Examples of the hetero atom in the aromatic hetero ringsinclude an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the above-describedaromatic hydrocarbon ring (an arylene group); and a group in which onehydrogen atom of a group (an aryl group) formed by removing one hydrogenatom from the aromatic hydrocarbon ring has been substituted with analkylene group (a group formed by removing one more hydrogen atom froman aryl group in an arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group(an alkyl chain in the arylalkyl group) has preferably 1 to 4 carbonatoms, more preferably 1 or 2 carbon atoms, and most preferably 1 carbonatom.

The constitutional unit (a0-1) included in the component (A1) may beused alone or two or more kinds thereof.

The proportion of the constitutional unit (a0-1) in the component (A1)is preferably in a range of 5% to 60% by mole, more preferably in arange of 5% to 55% by mole, still more preferably in a range of 10% to50% by mole, and particularly preferably in a range of 15% to 40% bymole with respect to the total amount (100% by mole) of allconstitutional units constituting the component (A1).

By setting the proportion of the constitutional unit (a0-1) to begreater than or equal to the lower limit, a resist pattern can be easilyobtained, and lithography characteristics such as the sensitivity, theresolution, and roughness reduction, and the like are improved.

Further, by setting the proportion of the constitutional unit (a0-1) tobe lower than or equal to the upper limit, the constitutional unit(a0-1) and other constitutional units can be balanced.

In regard to constitutional unit (a0-2):

The constitutional unit (a0-2) is a constitutional unit derived from acompound (hereinafter, also referred to as a “compound (a0)”)represented by Formula (a0-2).

[In the formula, W represents a polymerizable group-containing group.Ra⁰² represents an acid dissociable group represented by Formula(a02-r-1).]

[In the formula, Ra⁰²¹ and Ra⁰²² each independently represent a linearor branched aliphatic hydrocarbon group. Ra⁰²³ represents an aromatichydrocarbon group. The symbol “*” represents a bonding site.]

In Formula (a0-2), W represents a polymerizable group-containing groupand has the same definition as that for the polymerizable grouprepresented by W in Formula (a0-1).

In Formula (a0-2), Ra⁰² represents an acid dissociable group representedby Formula (a02-r-1).

In Formula (a02-r-1), Ra⁰²¹ and Ra⁰²² each independently represent alinear or branched aliphatic hydrocarbon group. Examples of the linearor branched aliphatic hydrocarbon group as Ra⁰²¹ and Ra⁰²² include thoseexemplified as the linear or branched aliphatic hydrocarbon groupsrepresented by Ra⁰¹¹ to Ra⁰¹³ in Formula (a01-r-1).

Among these, as Ra⁰²¹ and Ra⁰²², a linear alkyl group having 1 to 5carbon atoms is preferable, and a methyl group or an ethyl group is morepreferable.

In Formula (a02-r-1), Ra⁰²³ represents an aromatic hydrocarbon group.The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring. The aromatic ring is not particularly limited as longas it is a cyclic conjugated system having (4n+2) π electrons, and maybe monocyclic or polycyclic. The aromatic ring has preferably 5 to 30carbon atoms, more preferably 5 to 20 carbon atoms, still morepreferably 6 to 15 carbon atoms, and particularly preferably 6 to 12carbon atoms. Specific examples of the aromatic ring include aromatichydrocarbon rings such as benzene, naphthalene, anthracene, andphenanthrene; and aromatic hetero rings in which some carbon atomsconstituting the above-described aromatic hydrocarbon rings have beensubstituted with hetero atoms. Examples of the hetero atom in thearomatic hetero rings include an oxygen atom, a sulfur atom, and anitrogen atom. Specific examples of the aromatic hetero ring include apyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group as Ra⁰²³ include agroup in which one hydrogen atom has been removed from theabove-described aromatic hydrocarbon ring or aromatic hetero ring (anaryl group or a heteroaryl group); a group in which one hydrogen atomhas been removed from an aromatic compound having two or more aromaticrings (biphenyl, fluorene or the like); and a group in which onehydrogen atom of the above-described aromatic hydrocarbon ring oraromatic hetero ring has been substituted with an alkylene group (forexample, an arylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group which is bondedto the above-described aromatic hydrocarbon ring or aromatic hetero ringhas preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms,and particularly preferably 1 carbon atom.

Among these, a phenyl group or a naphthyl group is preferable as Ra⁰²³.

Specific examples of the acid dissociable group represented by Formula(a02-r-1) include the followings. The symbol “*” represents a bondingsite.

Among the examples, as the constitutional unit (a0-2), a constitutionalunit represented by Formula (a0-2-2) is preferable.

[In the formula, R represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms. Va⁰² represents a divalent hydrocarbon group which may have anether bond, and na₀₂ represent 0 or 2. Ra⁰²¹ represents an aciddissociable group represented by Formula (a02-r-11).]

[In the formula, Ra⁰²¹′ and Ra⁰²²′ each independently represent a methylgroup or an ethyl group. Ra⁰²³′ represents a phenyl group or a naphthylgroup. The symbol “*” represents a bonding site.]

In Formula (a0-2-2), R has the same definition as that for R in Formula(a0-2-1).

In Formula (a0-2-2), the divalent hydrocarbon group which may have anether bond as Va⁰² has the same definition as that for the divalenthydrocarbon group which may have an ether bond as Va⁰¹ in Formula(a0-1-1).

The constitutional unit (a0-2) included in the component (A1) may beused alone or two or more kinds thereof.

The proportion of the constitutional unit (a0-2) in the component (A1)is preferably in a range of 1% to 55% by mole, more preferably in arange of 1% to 50% by mole, still more preferably in a range of 5% to45% by mole, and particularly preferably in a range of 10% to 35% bymole with respect to the total amount (100% by mole) of allconstitutional units constituting the component (A1).

By setting the proportion of the constitutional unit (a0-2) to begreater than or equal to the lower limit, a resist pattern can be easilyobtained, and lithography characteristics such as the sensitivity, theresolution, and roughness reduction, and the like are improved.

Further, by setting the proportion of the constitutional unit (a0-2) tobe lower than or equal to the upper limit, the constitutional unit(a0-2) and other constitutional units can be balanced.

In regard to other constitutional units:

Such a component (A1) may have other constitutional units as necessaryin addition to the constitutional unit (a0).

Examples of other constitutional units include a constitutional unit(a10) represented by Formula (a10-1); a constitutional unit (a1)containing an acid decomposable group whose polarity is increased due toan action of an acid (here, excluding the constitutional unit (a0)); aconstitutional unit (a2) containing a lactone-containing cyclic group, a—SO₂-containing cyclic group, or a carbonate-containing cyclic group; aconstitutional unit (a3) containing a polar group-containing aliphatichydrocarbon group (here, excluding the constitutional unit (a1) or theconstitutional unit (a2)); a constitutional unit (a4) containing an acidundissociable aliphatic cyclic group; and a constitutional unit derivedfrom styrene or a derivative thereof.

In regard to constitutional unit (a10):

The constitutional unit (a10) is a constitutional unit represented byFormula (a10-1).

[In the formula, R represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms. Ya^(x1) represents a single bond or a divalent linking group.Wa^(x1) represents an (n_(ax1)+1)-valent aromatic hydrocarbon group.n_(ax1) represents an integer of 1 or greater.]

In Formula (a10-1), R represents a hydrogen atom, an alkyl group having1 to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms.

As the alkyl group having 1 to 5 carbon atoms represented by R, a linearor branched alkyl group having 1 to 5 carbon atoms is preferable, andspecific examples thereof include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group, and a neopentylgroup.

The halogenated alkyl group having 1 to 5 carbon atoms as R is a groupin which some or all hydrogen atoms of the above-described alkyl grouphaving 1 to 5 carbon atoms have been substituted with halogen atoms.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom, and a fluorine atom is particularlypreferable.

As R, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or afluorinated alkyl group having 1 to 5 carbon atoms is preferable, ahydrogen atom, a methyl group, or a trifluoromethyl group is morepreferable, a hydrogen atom or methyl group is still more preferable,and a methyl group is particularly preferable in terms of industrialavailability.

In Formula (a10-1), Ya^(x1) represents a single bond or a divalentlinking group.

In the chemical formula shown above, the divalent linking group asYa^(x1) is not particularly limited, and suitable examples thereofinclude a divalent hydrocarbon group which may have a substituent and adivalent linking group having hetero atoms.

Divalent Hydrocarbon Group which May have Substituent:

In a case where Ya^(x1) represents a divalent hydrocarbon group whichmay have a substituent, the hydrocarbon group may be an aliphatichydrocarbon group or an aromatic hydrocarbon group.

Aliphatic Hydrocarbon Group as Ya^(x1) The aliphatic hydrocarbon groupindicates a hydrocarbon group that has no aromaticity. The aliphatichydrocarbon group may be saturated or unsaturated. In general, thealiphatic hydrocarbon group is preferably saturated.

Examples of the aliphatic hydrocarbon group include a linear or branchedaliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

Linear or Branched Aliphatic Hydrocarbon Group

The linear aliphatic hydrocarbon group has preferably 1 to 10 carbonatoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4carbon atoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group has preferably 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, a branched alkylene groupis preferred, and specific examples thereof include alkylalkylenegroups, for example, alkylmethylene groups such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—;and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in the alkylalkylene group, alinear alkyl group having 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group having 1 to 5 carbon atoms which has beensubstituted with a fluorine atom, and a carbonyl group.

Aliphatic Hydrocarbon Group Containing Ring in Structure Thereof

Examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof include a cyclic aliphatic hydrocarbon group which mayhave a substituent containing a hetero atom in the ring structurethereof (a group in which two hydrogen atoms have been removed from analiphatic hydrocarbon ring), a group in which the cyclic aliphatichydrocarbon group is bonded to the terminal of a linear or branchedaliphatic hydrocarbon group, and a group in which the cyclic aliphatichydrocarbon group is interposed in a linear or branched aliphatichydrocarbon group. As the linear or branched aliphatic hydrocarbongroup, the same groups as those described above can be exemplified.

The cyclic aliphatic hydrocarbon group has preferably 3 to 20 carbonatoms and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which two hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane has preferably 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic alicyclic hydrocarbon group, a group in which two hydrogenatoms have been removed from a polycycloalkane is preferable. As thepolycycloalkane, a group having 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup, and a carbonyl group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group,an n-butyl group, or a tert-butyl group is particularly preferable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an iso-propoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom as the substituent include a fluorine atom,a chlorine atom, a bromine atom, and an iodine atom, and a fluorine atomis preferable.

Examples of the halogenated alkyl group as the substituent includegroups in which some or all hydrogen atoms in the above-described alkylgroups have been substituted with the above-described halogen atoms.

In the cyclic aliphatic hydrocarbon group, some carbon atomsconstituting the ring structure thereof may be substituted with asubstituent containing a hetero atom. As the substituent containing ahetero atom, —O—, —C(═O)—O—, —S—, —S(═O)₂—, or —S(═O)₂—O— is preferable.

Aromatic Hydrocarbon Group as Ya^(x1)

The aromatic hydrocarbon group is a hydrocarbon group having at leastone aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclicconjugated system having (4n+2) π electrons, and may be monocyclic orpolycyclic. The aromatic ring has preferably 5 to 30 carbon atoms, morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 12 carbon atoms. Here, the number ofcarbon atoms in a substituent is not included in the number of carbonatoms.

Examples of the aromatic ring include aromatic hydrocarbon rings such asbenzene, naphthalene, anthracene, and phenanthrene; and aromatic heterorings in which some carbon atoms constituting the above-describedaromatic hydrocarbon rings have been substituted with hetero atoms.Examples of the hetero atom in the aromatic hetero rings include anoxygen atom, a sulfur atom, and a nitrogen atom. Specific examples ofthe aromatic hetero ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the above-describedaromatic hydrocarbon ring or aromatic hetero ring (an arylene group or aheteroarylene group); a group in which two hydrogen atoms have beenremoved from an aromatic compound having two or more aromatic rings(biphenyl, fluorene or the like); and a group in which one hydrogen atomof a group (an aryl group or a heteroaryl group) formed by removing onehydrogen atom from the above-described aromatic hydrocarbon ring oraromatic hetero ring has been substituted with an alkylene group (agroup in which one hydrogen atom has been further removed from the arylgroup in the above-described arylalkyl group such as a benzyl group, aphenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene groupwhich is bonded to the above-described aryl group or heteroaryl grouphas preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms,and most preferably 1 carbon atom.

With respect to the aromatic hydrocarbon group, the hydrogen atom in thearomatic hydrocarbon group may be substituted with a substituent. Forexample, the hydrogen atom bonded to the aromatic ring in the aromatichydrocarbon group may be substituted with a substituent. Examples ofsubstituents include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, and a hydroxyl group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group,an n-butyl group, or a tert-butyl group is more preferable.

As the alkoxy group, the halogen atom, and the halogenated alkyl groupas the substituents, the same groups as the above-described substituentgroups for substituting a hydrogen atom in the cyclic aliphatichydrocarbon group can be exemplified.

Divalent Linking Group Containing Hetero Atom:

In a case where Ya^(x1) represents a divalent linking group containing ahetero atom, preferred examples of the linking group include —O—,—C(═O)—O—, —O—C(═O)—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (H may be substituted with a substituent such as an alkylgroup, an acyl group, or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by Formula: —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—,—C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²— or—Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²² each independentlyrepresent a divalent hydrocarbon group which may have a substituent, Orepresents an oxygen atom, and m″ represents an integer of 0 to 3].

In a case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH—, or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group, or the like.The substituent (an alkyl group, an acyl group, or the like) haspreferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms,and most preferably 1 to 5 carbon atoms.

In Formula —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²—, or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represent a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe above-described divalent linking group As Ya^(x1).

As Y²¹, a linear aliphatic hydrocarbon group is preferable, a linearalkylene group is more preferable, a linear alkylene group having 1 to 5carbon atoms is still more preferable, and a methylene group or anethylene group is particularly preferable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group, or an alkylmethylene group ismore preferable. The alkyl group in the alkylmethylene group ispreferably a linear alkyl group having 1 to 5 carbon atoms, morepreferably a linear alkyl group having 1 to 3 carbon atoms, and mostpreferably a methyl group.

In the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and particularly preferably 1. In other words, it isparticularly preferable that the group represented by Formula—[Y²¹—C(═O)—O]_(m″)—Y²²— represents a group represented by Formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by Formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′represents an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1. b′ represents an integer of 1 to 10, preferably an integerof 1 to 8, more preferably an integer of 1 to 5, still more preferably 1or 2, and most preferably 1.

In the description above, as Ya^(x1), a single bond, an ester bond[—C(═O)—O— or —O—C(═O)—], an ether bond (—O—), a linear or branchedalkylene group, or a combination of these is preferable, and a singlebond or an ester bond [—C(═O)—O— or —O—C(═O)—] is more preferable.

In Formula (a10-1), Wa^(x1) represents an (n_(ax1)+1)-valent aromatichydrocarbon group.

Examples of the aromatic hydrocarbon group as Wa^(x1) include a groupformed by removing (n_(ax1)+1) hydrogen atoms from an aromatic ring. Thearomatic ring is not particularly limited as long as it is a cyclicconjugated system having (4n+2) π electrons, and may be monocyclic orpolycyclic. The aromatic ring has preferably 5 to 30 carbon atoms, morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and particularly preferably 6 to 12 carbon atoms. Specificexamples of the aromatic ring include aromatic hydrocarbon rings such asbenzene, naphthalene, anthracene, and phenanthrene; and aromatic heterorings in which some carbon atoms constituting the above-describedaromatic hydrocarbon rings have been substituted with hetero atoms.Examples of the hetero atom in the aromatic hetero rings include anoxygen atom, a sulfur atom, and a nitrogen atom. Specific examples ofthe aromatic hetero ring include a pyridine ring and a thiophene ring.

Examples of the aromatic hydrocarbon group as Wa^(x1) include a groupformed by removing (n_(ax1)+1) hydrogen atoms from an aromatic compound(such as biphenyl or fluorene) having two or more aromatic ring.

Among these, as Wa^(x1), a group formed by removing (n_(ax1)+1) hydrogenatoms from benzene, naphthalene, anthracene, or biphenyl is preferable,a group formed by removing (n_(ax1)+1) hydrogen atoms from benzene ornaphthalene is more preferable, and a group formed by removing(n_(ax1)+1) hydrogen atoms from benzene.

In Formula (a10-1), n_(ax1) represents an integer of 1 or greater,preferably an integer of 1 to 10, more preferably an integer of 1 to 5,still more preferably 1, 2, or 3, and particularly preferably 1 or 2.

Hereinafter, specific examples of the constitutional unit (a10)represented by Formula (a10-1) are described.

In each formula shown below, R^(α) represents a hydrogen atom, a methylgroup, or a trifluoromethyl group.

The constitutional unit (a10) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (a10),the proportion of the constitutional unit (a10) in the component (A1) ispreferably in a range of 20% to 80% by mole, more preferably in a rangeof 20% to 70% by mole, still more preferably in a range of 25% to 60% bymole, and particularly preferably in a range of 30% to 50% by mole withrespect to the total amount (100% by mole) of all constitutional unitsin the component (A1).

By setting the proportion of the constitutional unit (a10) to be greaterthan or equal to the lower limit, the sensitivity can be easilyimproved.

Further, by setting the proportion of the constitutional unit (a10) tobe lower than or equal to the upper limit, the constitutional unit (a10)and other constitutional units can be balanced.

In regard to constitutional unit (a1):

The component (A1) may further have a constitutional unit (a1) (here,excluding the constitutional unit (a0)) containing an acid decomposablegroup whose polarity is increased due to the action of an acid, inaddition to the constitutional unit (a0).

The term “acid decomposable group” indicates a group in which at least apart of a bond in the structure of the acid decomposable group can becleaved due to the action of an acid.

Examples of the acid decomposable group whose polarity is increased dueto the action of an acid include groups which are decomposed due to theaction of an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxyl group,an amino group, and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereinafter, also referred toas a “OH-containing polar group”) is preferable, a carboxy group or ahydroxyl group is more preferable, and a carboxy group is particularlypreferable.

More specific examples of the acid decomposable group include a group inwhich the above-described polar group has been protected with an aciddissociable group (such as a group in which a hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup).

Here, the “acid dissociable group” indicates both (i) group in which abond between the acid dissociable group and an atom adjacent to the aciddissociable group can be cleaved due to the action of an acid; and (ii)group in which some bonds are cleaved due to the action of an acid, andthen a decarboxylation reaction occurs, thereby cleaving the bondbetween the acid dissociable group and the atom adjacent to the aciddissociable group.

It is necessary that the acid dissociable group that constitutes theacid decomposable group is a group which exhibits a lower polarity thanthe polar group generated by the dissociation of the acid dissociablegroup. Thus, in a case where the acid dissociable group is dissociatedby the action of an acid, a polar group exhibiting a higher polaritythan that of the acid dissociable group is generated, thereby increasingthe polarity. As a result, the polarity of the entire component (A1) isincreased. By the increase in the polarity, relatively, the solubilityin a developing solution changes, and the solubility in an alkalideveloping solution is increased, whereas the solubility in an organicdeveloping solution is relatively decreased.

Examples of the acid dissociable group in the constitutional unit (a1)include groups which have been proposed as acid dissociable groups ofthe base resin for a conventional chemically amplified resistcomposition, excluding tertiary carbon atom-containing groups in Formula(a0-1).

Specific examples of acid dissociable groups for the base resin of aconventional chemically amplified resist composition include an “acetaltype acid dissociable group”, a “tertiary alkyl ester type aciddissociable group”, and a “tertiary alkyloxycarbonyl acid dissociablegroup” described below.

Acetal Type Acid Dissociable Group:

Examples of the acid dissociable group for protecting a carboxy group ora hydroxyl group as a polar group include the acid dissociable grouprepresented by Formula (a1-r-1) shown below (hereinafter, also referredto as “acetal type acid dissociable group”).

[In the formula, Ra′¹ and Ra′² represents a hydrogen atom or an alkylgroup, and Ra′³ represents a hydrocarbon group, provided that Ra′³ maybe bonded to Ra′¹ or Ra′².]

In Formula (a1-r-1), it is preferable that at least one of Ra′¹ and Ra′²represents a hydrogen atom and more preferable that both of Ra′¹ andRa′² represent a hydrogen atom.

In a case where Ra′¹ or Ra′² represents an alkyl group, examples of thealkyl group include the same alkyl groups exemplified as the substituentwhich may be bonded to the carbon atom at the α-position in thedescription on α-substituted acrylic acid ester. Among these, an alkylgroup having 1 to 5 carbon atoms is preferable. Specific examplesthereof include linear or branched alkyl groups. Specific examples ofthe alkyl group include a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, and a neopentyl group. Amongthese, a methyl group or an ethyl group is preferable, and a methylgroup is particularly preferable.

In Formula (a1-r-1), examples of the hydrocarbon group as Ra′³ include alinear or branched alkyl group and a cyclic hydrocarbon group.

The linear alkyl group has preferably 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesthereof include a methyl group, an ethyl group, an n-propyl group, ann-butyl group, and an n-pentyl group. Among these, a methyl group, anethyl group, or an n-butyl group is preferable, and a methyl group or anethyl group is more preferable.

The branched alkyl group has preferably 3 to 10 carbon atoms and morepreferably 3 to 5 carbon atoms. Specific examples thereof include anisopropyl group, an isobutyl group, a tert-butyl group, an isopentylgroup, a neopentyl group a 1,1-diethylpropyl group, and a2,2-dimethylbutyl group. Among these, an isopropyl group is preferable.

In a case where Ra′³ represents a cyclic hydrocarbon group, the cyclichydrocarbon group may be an aliphatic hydrocarbon group or an aromatichydrocarbon group, and may be polycyclic or monocyclic.

As the aliphatic hydrocarbon group which is a monocyclic group, a groupin which one hydrogen atom has been removed from a monocycloalkane ispreferable. The monocycloalkane has preferably 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane.

As the aliphatic hydrocarbon group which is a polycyclic group, a groupin which one hydrogen atom has been removed from a polycycloalkane ispreferable. As the polycycloalkane, a group having 7 to 12 carbon atomsis preferable. Specific examples of the polycycloalkane includeadamantane, norbornane, isobornane, tricyclodecane, andtetracyclododecane.

In a case where the cyclic hydrocarbon group as Ra′³ becomes an aromatichydrocarbon group, the aromatic hydrocarbon group is a hydrocarbon grouphaving at least one aromatic ring.

The aromatic ring is not particularly limited as long as it is a cyclicconjugated system having (4n+2) π electrons, and may be monocyclic orpolycyclic. The aromatic ring has preferably 5 to 30 carbon atoms, morepreferably 5 to 20 carbon atoms, still more preferably 6 to 15 carbonatoms, and most preferably 6 to 12 carbon atoms. Specific examples ofthe aromatic ring include aromatic hydrocarbon rings such as benzene,naphthalene, anthracene, and phenanthrene; and aromatic hetero rings inwhich some carbon atoms constituting the above-described aromatichydrocarbon rings have been substituted with hetero atoms. Examples ofthe hetero atom in the aromatic hetero rings include an oxygen atom, asulfur atom, and a nitrogen atom. Specific examples of the aromatichetero ring include a pyridine ring and a thiophene ring.

Specific examples of the aromatic hydrocarbon group as Ra′³ include agroup in which one hydrogen atom has been removed from theabove-described aromatic hydrocarbon ring or aromatic hetero ring (anaryl group or a heteroaryl group); a group in which one hydrogen atomhas been removed from an aromatic compound having two or more aromaticrings (biphenyl, fluorene or the like); and a group in which onehydrogen atom of the above-described aromatic hydrocarbon ring oraromatic hetero ring has been substituted with an alkylene group (anarylalkyl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group which is bondedto the above-described aromatic hydrocarbon ring or aromatic hetero ringhas preferably 1 to 4 carbon atoms, more preferably 1 or 2 carbon atoms,and particularly preferably 1 carbon atom.

In a case where Ra′³ is bonded to Ra′¹ or Ra′² to form a ring, thecyclic group is preferably a 4- to 7-membered ring, and more preferablya 4- to 6-membered ring. Specific examples of the cyclic group include atetrahydropyranyl group and a tetrahydrofuranyl group.

Tertiary Alkyl Ester Type Acid Dissociable Group:

Examples of the acid dissociable group for protecting the carboxy groupas a polar group include the acid dissociable group represented byFormula (a1-r-2) shown below. Among the acid dissociable groupsrepresented by Formula (a1-r-2), for convenience, a group which isconstituted of alkyl groups is referred to as “tertiary alkyl ester typeacid dissociable group”.

[In the formula, Ra′⁴ to Ra′⁶ each independently represent a hydrocarbongroup, provided that Ra′⁵ and Ra′⁶ may be bonded to each other to form aring.]

Examples of the hydrocarbon groups as Ra′⁴ to Ra′⁶ include thoserepresented by Ra′³ and a chain-like alkenyl group. Such a chain-likealkenyl group may be linear or branched, and the number of carbon atomsthereof is preferably in a range of 2 to 10, more preferably in a rangeof 2 to 5, still more preferably in a range of 2 to 4, and particularlypreferably 3. Examples of the linear alkenyl group include a vinylgroup, a propenyl group (an allyl group), and a butynyl group. Examplesof the branched alkenyl group include a 1-methylvinyl group, a2-methylvinyl group, a 1-methylpropenyl group, and a 2-methylpropenylgroup. Among the examples, as the chain-like alkenyl group, a linearalkenyl group is preferable, a vinyl group or a propenyl group is morepreferable, and a vinyl group is particularly preferable.

It is preferable that Ra′⁴ represents a group (an aryl group or aheteroaryl group) formed by removing one hydrogen atom from an aromatichydrocarbon ring or an aromatic hetero ring or an alkyl group having 1to 5 carbon atoms. In a case where Ra′⁵ and Ra′⁶ are bonded to eachother to form a ring, a group represented by Formula (a1-r2-1) shownbelow can be exemplified. On the other hand, in a case where Ra′⁴ toRa′⁶ are not bonded to each other and independently represent ahydrocarbon group, a group represented by Formula (a1-r2-2) shown belowcan be exemplified.

[In the formulae, Ra′¹⁰ represents a hydrocarbon group having 1 to 10carbon atoms, Ra′¹¹ represents a group that forms an aliphatic cyclicgroup together with a carbon atom to which Ra′¹⁰ is bonded, and Ra′¹² toRa′¹⁴ each independently represent a hydrocarbon group.]

In Formula (a1-r2-1), as the hydrocarbon group having 1 to 10 carbonatoms as Ra′¹⁰, the same groups as described above for the linear orbranched alkyl group as Ra′³ in Formula (a1-r-1) are preferable.

In Formula (a1-r2-1), as the aliphatic cyclic group that is formed byRa′¹¹ together with the carbon atom to which Ra′¹⁰ is bonded, the samegroups as those described above for the monocyclic or polycyclicaliphatic hydrocarbon group as Ra′³ in Formula (a1-r-1) are preferable.Further, a heterocyclic group in which some carbon atoms constitutingthe aliphatic hydrocarbon group which is a monocyclic group or apolycyclic group has been substituted with hetero atoms may beexemplified. Examples of the hetero atoms in this heterocyclic groupinclude an oxygen atom, a sulfur atom, and a nitrogen atom.

In Formula (a1-r2-2), it is preferable that Ra′¹² and Ra′¹⁴ eachindependently represent an alkyl group having 1 to 10 carbon atoms, andit is more preferable that the alkyl group is the same group as thedescribed above for the linear or branched alkyl group as Ra′³ inFormula (a1-r-1), it is still more preferable that the alkyl group is alinear alkyl group having 1 to 5 carbon atoms, and it is particularlypreferable that the alkyl group is a methyl group or an ethyl group.

In Formula (a1-r2-2), it is preferable that Ra′¹³ is the same group asdescribed above for the linear or branched alkyl group or monocyclic orpolycyclic aliphatic hydrocarbon group as Ra′³ in Formula (a1-r-1).Among these examples, a group exemplified as the aliphatic hydrocarbongroup which is a monocyclic group or a polycyclic group as Ra′³ is morepreferable. Further, a heterocyclic group in which some carbon atomsconstituting the aliphatic hydrocarbon group which is a monocyclic groupor a polycyclic group has been substituted with hetero atoms may beexemplified. Examples of the hetero atoms in this heterocyclic groupinclude an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the group represented by Formula (a1-r2-1) areshown below. The symbol “*” represents a bonding site.

Specific examples of the group represented by Formula (a1-r2-2) areshown below.

Tertiary Alkyloxycarbonyl Acid Dissociable Group

Examples of the acid dissociable group for protecting a hydroxyl groupas a polar group include an acid dissociable group (hereinafter, forconvenience, also referred to as “tertiary alkyloxycarbonyl type aciddissociable group”) represented by Formula (a1-r-3) shown below.

[In the formula, Ra′⁷ to Ra′⁹ each independently represent an alkylgroup.]

In Formula (a1-r-3), Ra′⁷ to Ra′⁹ each independently representpreferably an alkyl group having 1 to 5 carbon atoms and more preferablyan alkyl group having 1 to 3 carbon atoms.

Further, the total number of carbon atoms in each alkyl group ispreferably in a range of 3 to 7, more preferably in a range of 3 to 5,and still more preferably 3 or 4.

Examples of the constitutional unit (a1) include a constitutional unitderived from acrylic acid ester in which the hydrogen atom bonded to thecarbon atom at the α-position may be substituted with a substituent; aconstitutional unit derived from acrylamide; a constitutional unit inwhich at least some hydrogen atoms in a hydroxyl group of aconstitutional unit derived from hydroxystyrene or a hydroxystyrenederivative are protected by a substituent containing the aciddecomposable group; and a constitutional unit in which some hydrogenatoms in —C(═O)—OH of a constitutional unit derived from vinylbenzoicacid or a vinylbenzoic acid derivative are protected by a substituentcontaining the acid decomposable group.

Among the examples, as the constitutional unit (a1), a constitutionalunit derived from acrylic acid ester in which the hydrogen atom bondedto the carbon atom at the α-position may be substituted with asubstituent is preferable.

Specific preferred examples of such a constitutional unit (a1) includeconstitutional units represented by Formula (a1-1) or (a1-2) shownbelow.

[In the formula, R represents a hydrogen atom, an alkyl group having 1to 5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbonatoms, Va¹ represents a divalent hydrocarbon group which may contain anether bond, n_(a1) represents an integer of 0 to 2, and Ra¹ representsan acid dissociable group represented by Formula (a1-r-1) or (a1-r-2).Wa¹ represents a (n_(a2)+1)-valent hydrocarbon group, n_(a2) representsan integer of 1 to 3, and Ra² represents an acid dissociable grouprepresented by Formula (a1-r-1) or (a1-r-3)].

In Formula (a1-1), R has the same definition as that for R in Formula(a0-1-1).

In Formula (a1-1), the divalent hydrocarbon group which may have anether bond as Va¹ has the same definition as that for the divalenthydrocarbon group which may have an ether bond as V0⁰¹ in Formula(a0-1-1)

In Formula (a1-1), Va¹ represents a divalent hydrocarbon group which mayhave an ether bond. The divalent hydrocarbon group as V^(a1) may be analiphatic hydrocarbon group or an aromatic hydrocarbon group.

The aliphatic hydrocarbon group as the divalent hydrocarbon grouprepresented by Va¹ may be saturated or unsaturated. In general, thealiphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof.

The linear aliphatic hydrocarbon group has preferably 1 to 10 carbonatoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4carbon atoms, and most preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], and a pentamethylene group [—(CH₂)₅—].

The branched aliphatic hydrocarbon group has preferably 2 to 10 carbonatoms, more preferably 3 to 6 carbon atoms, still more preferably 3 or 4carbon atoms, and most preferably 3 carbon atoms.

As the branched aliphatic hydrocarbon group, a branched alkylene groupis preferred, and specific examples thereof include alkylalkylenegroups, for example, alkylmethylene groups such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—;and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in the alkylalkylene group, alinear alkyl group having 1 to 5 carbon atoms is preferable.

Examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof include an alicyclic hydrocarbon group (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), a group in which the alicyclic hydrocarbon group is bonded to theterminal of the linear or branched aliphatic hydrocarbon group, and agroup in which the alicyclic hydrocarbon group is interposed in theabove-described linear or branched aliphatic hydrocarbon group. Thelinear or branched aliphatic hydrocarbon group is the same as definedfor the above-described linear aliphatic hydrocarbon group or theabove-described branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group has preferably 3 to 20 carbon atoms andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic. As themonocyclic alicyclic hydrocarbon group, a group in which two hydrogenatoms have been removed from a monocycloalkane is preferable. Themonocycloalkane has preferably 3 to 6 carbon atoms, and specificexamples thereof include cyclopentane and cyclohexane. As the polycyclicalicyclic hydrocarbon group, a group in which two hydrogen atoms havebeen removed from a polycycloalkane is preferable. As thepolycycloalkane, a group having 7 to 12 carbon atoms is preferable.Specific examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane, and tetracyclododecane.

The aromatic hydrocarbon group as the divalent hydrocarbon grouprepresented by Va¹ is a hydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group has preferably 3 to 30 carbon atoms, morepreferably 5 to 30 carbon atoms, still more preferably 5 to 20 carbonatoms, particularly preferably 6 to 15 carbon atoms, and most preferably6 to 10 carbon atoms. Here, the number of carbon atoms in a substituentis not included in the number of carbon atoms.

Specific examples of the aromatic ring contained in the aromatichydrocarbon group include aromatic hydrocarbon rings such as benzene,biphenyl, fluorene, naphthalene, anthracene, and phenanthrene; andaromatic hetero rings in which some carbon atoms constituting theabove-described aromatic hydrocarbon rings have been substituted withhetero atoms. Examples of the hetero atom in the aromatic hetero ringsinclude an oxygen atom, a sulfur atom, and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the above-describedaromatic hydrocarbon ring (an arylene group); and a group in which onehydrogen atom of a group (an aryl group) formed by removing one hydrogenatom from the aromatic hydrocarbon ring has been substituted with analkylene group (a group formed by removing one more hydrogen atom froman aryl group in an arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group, or a 2-naphthylethyl group). The alkylene group(an alkyl chain in the arylalkyl group) has preferably 1 to 4 carbonatoms, more preferably 1 or 2 carbon atoms, and particularly preferably1 carbon atom.

In Formula (a1-2), the (n_(a2)+1)-valent hydrocarbon group as Wa¹ may bean aliphatic hydrocarbon group or an aromatic hydrocarbon group. Thealiphatic hydrocarbon group indicates a hydrocarbon group that has noaromaticity, and may be saturated or unsaturated, but is preferablysaturated. Examples of the aliphatic hydrocarbon group include a linearor branched aliphatic hydrocarbon group, an aliphatic hydrocarbon groupcontaining a ring in the structure thereof, and a combination of thelinear or branched aliphatic hydrocarbon group and the aliphatichydrocarbon group containing a ring in the structure thereof.

The valency of n_(a2)+1 is preferably divalent, trivalent ortetravalent, and divalent or trivalent is more preferable.

Specific examples of the constitutional unit represented by Formula(a1-1) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup, or a trifluoromethyl group.

Specific examples of the constitutional unit represented by Formula(a1-2) are shown below.

The constitutional unit (a1) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (a1), theproportion of the constitutional unit (a1) in the component (A1) ispreferably in a range of 1% to 50% by mole, more preferably in a rangeof 5% to 45% by mole, and still more preferably in a range of 5% to 30%by mole with respect to the total amount (100% by mole) of allconstitutional units constituting the component (A1).

By setting the proportion of the constitutional unit (a1) to be greaterthan or equal to the lower limit, a resist pattern can be easilyobtained, and lithography characteristics such as the sensitivity, theresolution, and roughness reduction, and the like are improved. Further,by setting the proportion of the constitutional unit (a1) to be lowerthan or equal to the upper limit, the constitutional unit (a1) and otherconstitutional units can be balanced.

In regard to constitutional unit (a2):

The component (A1) may have a constitutional unit (a2) containing alactone-containing cyclic group, a —SO₂-containing cyclic group, or acarbonate-containing cyclic group in addition to the constitutionalunits (a0-1) and (a0-2).

In a case where the component (A1) is used for forming a resist film,the lactone-containing cyclic group, the —SO₂-containing cyclic group,or the carbonate-containing cyclic group in the constitutional unit (a2)is effective for improving the adhesiveness of the resist film to thesubstrate. Further, by virtue of including the constitutional unit (a2),in an alkali developing process, during developing, the solubility ofthe resist film in an alkali developing solution is enhanced.

The term “lactone-containing cyclic group” indicates a cyclic group thatcontains a ring (lactone ring) containing a —O—C(═O)— in the ringstructure. In a case where the lactone ring is counted as the first ringand the group contains only the lactone ring, the group is referred toas a monocyclic group. Further, in a case where the group has other ringstructures, the group is referred to as a polycyclic group regardless ofthe structures. The lactone-containing cyclic group may be a monocyclicgroup or a polycyclic group.

The lactone-containing cyclic group for the constitutional unit (a2) isnot particularly limited, and an optional constitutional unit may beused. Specific examples thereof include groups represented by Formulae(a2-r-1) to (a2-r-7) shown below.

[In the formulae, each Ra′²¹ independently represents a hydrogen atom,an alkyl group, an alkoxy group, a halogen atom, a halogenated alkylgroup, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or acyano group; and R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora —SO₂-containing cyclic group; A″ represents an oxygen atom (—O—), asulfur atom (—S—) or an alkylene group having 1 to 5 carbon atoms whichmay contain an oxygen atom or a sulfur atom; n′ represents an integer of0 to 2; and m′ represents 0 or 1.]

In Formulae (a2-r-1) to (a2-r-7), the alkyl group as Ra′²¹ is preferablyan alkyl group having 1 to 6 carbon atoms. Further, the alkyl group ispreferably a linear alkyl group or a branched alkyl group. Specificexamples thereof include a methyl group, an ethyl group, a propyl group,an isopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group, a neopentyl group, and ahexyl group. Among these, a methyl group or ethyl group is preferable,and a methyl group is particularly preferable.

The alkoxy group as Ra′²¹ is preferably an alkoxy group having 1 to 6carbon atoms.

Further, the alkoxy group is preferably a linear or branched alkoxygroup.

Specific examples of the alkoxy groups include a group formed by linkingthe above-described alkyl group as Ra′²¹ to an oxygen atom (—O—).

Examples of the halogen atom as Ra′²¹ include a fluorine atom, achlorine atom, a bromine atom, and an iodine atom. Among these, afluorine atom is preferable.

Examples of the halogenated alkyl group as Ra′²¹ include groups in whichsome or all hydrogen atoms in the above-described alkyl group as Ra′²¹have been substituted with the above-described halogen atoms. As thehalogenated alkyl group, a fluorinated alkyl group is preferable, and aperfluoroalkyl group is particularly preferable.

In —COOR″ and —OC(═O)R″ as Ra′²¹, R″ represents a hydrogen atom, analkyl group, a lactone-containing cyclic group, a carbonate-containingcyclic group, or a —SO₂-containing cyclic group.

The alkyl group as R″ may be linear, branched, or cyclic, and preferablyhas 1 to 15 carbon atoms.

In a case where R″ represents a linear or branched alkyl group, it ispreferably an alkyl group having 1 to 10 carbon atoms, more preferablyan alkyl group having 1 to 5 carbon atoms, and most preferably a methylgroup or an ethyl group.

In a case where R″ represents a cyclic alkyl group, the number of carbonatoms thereof is preferably in a range of 3 to 15, more preferably in arange of 4 to 12, and still more preferably in a range of 5 to 10.Specific examples thereof include groups in which one or more hydrogenatoms have been removed from a monocycloalkane, which may or may not besubstituted with a fluorine atom or a fluorinated alkyl group; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as bicycloalkane, tricycloalkane, ortetracycloalkane. More specific examples thereof include groups in whichone or more hydrogen atoms have been removed from a monocycloalkane suchas cyclopentane or cyclohexane; and groups in which one or more hydrogenatoms have been removed from a polycycloalkane such as adamantane,norbornane, isobornane, tricyclodecane, or tetracyclododecane.

Examples of the lactone-containing cyclic group as R″ include thoseexemplified as the groups represented by Formulae (a2-r-1) to (a2-r-7).

The carbonate-containing cyclic group as R″ has the same definition asthat for the carbonate-containing cyclic group described below. Specificexamples of the carbonate-containing cyclic group include groupsrepresented by Formulae (ax3-r-1) to (ax3-r-3).

The —SO₂-containing cyclic group as R″ has the same definition as thatfor the —SO₂-containing cyclic group described below. Specific examplesof the —SO₂-containing cyclic group include groups represented byFormulae (a5-r-1) to (a5-r-4).

The hydroxyalkyl group as Ra′²¹ has preferably 1 to 6 carbon atoms, andspecific examples thereof include a group in which at least one hydrogenatom in the alkyl group as Ra′²¹ has been substituted with a hydroxylgroup.

In Formulae (a2-r-2), (a2-r-3) and (a2-r-5), as the alkylene grouphaving 1 to 5 carbon atoms as A″, a linear or branched alkylene group ispreferable, and examples thereof include a methylene group, an ethylenegroup, an n-propylene group, and an isopropylene group. Examples ofalkylene groups that contain an oxygen atom or a sulfur atom includegroups in which —O— or —S— is interposed in the terminal of the alkylenegroup or between the carbon atoms of the alkylene group, and examplesthereof include —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—. As A″,an alkylene group having 1 to 5 carbon atoms or —O— is preferable, analkylene group having 1 to 5 carbon atoms is more preferable, and amethylene group is most preferable.

Specific examples of the groups represented by Formulae (a2-r-1) to(a2-r-7) are shown below.

containing —SO₂— in the ring structure thereof. Specifically, the—SO₂-containing cyclic group is a cyclic group in which the sulfur atom(S) in —SO₂— forms a part of the ring skeleton of the cyclic group. In acase where the ring containing —SO₂— in the ring skeleton thereof iscounted as the first ring and the group contains only the ring, thegroup is referred to as a monocyclic group. Further, in a case where thegroup has other ring structures, the group is referred to as apolycyclic group regardless of the structures. The —SO₂-containingcyclic group may be a monocyclic group or a polycyclic group.

As the —SO₂-containing cyclic group, a cyclic group containing —O—SO₂—in the ring skeleton thereof, in other words, a cyclic group containinga sultone ring in which —O—S— in the —O—SO₂— group forms a part of thering skeleton thereof is particularly preferable.

More specific examples of the —SO₂-containing cyclic group includegroups represented by Formulae (a5-r-1) to (a5-r-4) shown below.

[In the formulae, each Ra′⁵¹ independently represents a hydrogen atom,an alkyl group, an alkoxy group, a halogen atom, a halogenated alkylgroup, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group, or acyano group. R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora —SO₂-containing cyclic group. A″ represents an oxygen atom, a sulfuratom or an alkylene group having 1 to 5 carbon atoms which may containan oxygen atom or a sulfur atom. n′ represents an integer of 0 to 2.]

In Formulae (a5-r-1) and (a5-r-2), A″ has the same definition as thatfor A″ in Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, thehalogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl groupas Ra′⁵¹ include the same groups as those described above in theexplanation of Ra′²¹ in Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by Formulae (a5-r-1) to(a5-r-4) are shown below. In the formulae shown below, “Ac” representsan acetyl group.

The “carbonate-containing cyclic group” indicates a cyclic group havinga ring (a carbonate ring) containing —O—C(═O)—O— in the ring structurethereof. In a case where the carbonate ring is counted as the first ringand the group contains only the carbonate ring, the group is referred toas a monocyclic group. Further, in a case where the group has other ringstructures, the group is referred to as a polycyclic group regardless ofthe structures. The carbonate-containing cyclic group may be amonocyclic group or a polycyclic group.

The carbonate ring-containing cyclic group is not particularly limited,and an optional group may be used. Specific examples thereof includegroups represented by Formulae (ax3-r-1) to (ax3-r-3) shown below.

[In the formulae, each Ra′^(x31) independently represents a hydrogenatom, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, —COOR″, —OC(═O)R″, a hydroxyalkyl group,or a cyano group. R″ represents a hydrogen atom, an alkyl group, alactone-containing cyclic group, a carbonate-containing cyclic group, ora —SO₂-containing cyclic group. A″ represents an oxygen atom, a sulfuratom or an alkylene group having 1 to 5 carbon atoms which may containan oxygen atom or a sulfur atom. p′ represents an integer of 0 to 3, andq′ represents 0 or 1.]

In Formulae (ax3-r-2) and (ax3-r-3), A″ has the same definition as thatfor A″ in Formulae (a2-r-2), (a2-r-3) and (a2-r-5).

Examples of the alkyl group, the alkoxy group, the halogen atom, thehalogenated alkyl group, —COOR″, —OC(═O)R″, and the hydroxyalkyl groupas Ra′³¹ include the same groups as those described above in theexplanation of Ra′²¹ in Formulae (a2-r-1) to (a2-r-7).

Specific examples of the groups represented by Formulae (ax3-r-1) to(ax3-r-3) are shown below.

As the constitutional unit (a2), a constitutional unit derived fromacrylic acid ester in which the hydrogen atom bonded to the carbon atomat the α-position may be substituted with a substituent is preferable.

Specific preferred examples of such a constitutional unit (a2) include aconstitutional unit represented by Formula (a2-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group having 1 to5 carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms.Ya²¹ represents a single bond or a divalent linking group. La²¹represents —O—, —COO—, —CON(R′)—, —OCO—, —CONHCO— or —CONHCS—. R′represents a hydrogen atom or a methyl group; provided that, in a casewhere La²¹ represents —O—, Ya²¹ does not represents —CO—. Ra²¹represents a lactone-containing cyclic group, a carbonate-containingcyclic group, or a —SO₂-containing cyclic group.]

In Formula (a2-1), R has the same definition as described above.

As R, a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, or afluorinated alkyl group having 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly preferable in terms ofindustrial availability.

In Formula (a2-1), the divalent linking group as Ya²¹ is notparticularly limited, and suitable examples thereof include a divalenthydrocarbon group which may have a substituent and a divalent linkinggroup having hetero atoms.

Examples of the divalent hydrocarbon group as Ya²¹ include the samegroups exemplified for the divalent hydrocarbon group as Va¹ in Formula(a1-1). Examples of the substituent which may be included in thedivalent hydrocarbon group as Ya²¹ include an alkyl group having 1 to 5carbon atoms, an alkoxy group, a halogen atom, a halogenated alkyl grouphaving 1 to 5 carbon atoms, a hydroxyl group, and a carbonyl group.

Preferred examples of the divalent linking group having a hetero atom asYa²¹ include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—,—NH—C(═NH)— (H may be substituted with a substituent such as an alkylgroup, an acyl group, or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, and agroup represented by Formula —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—,—C(═O)—O—Y²¹—, —[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²—, or—Y²¹—S(═O)₂—O—Y²²— [in the formulae, Y²¹ and Y²² each independentlyrepresent a divalent hydrocarbon group which may have a substituent, Orepresents an oxygen atom, and m″ represents an integer of 0 to 3].

In a case where the divalent linking group containing a hetero atom is—C(═O)—NH—, —C(═O)—NH—C(═O)—, —NH—, or —NH—C(═NH)—, H may be substitutedwith a substituent such as an alkyl group, an acyl group, or the like.The substituent (an alkyl group, an acyl group, or the like) haspreferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms,and most preferably 1 to 5 carbon atoms.

In Formula —Y²¹—O—Y²²—, —Y²¹—O—, —Y²¹—C(═O)—O—, —C(═O)—O—Y²¹—,—[Y²¹—C(═O)—O]_(m″)—Y²²—, —Y²¹—O—C(═O)—Y²²—, or —Y²¹—S(═O)₂—O—Y²²—, Y²¹and Y²² each independently represent a divalent hydrocarbon group whichmay have a substituent. Examples of the divalent hydrocarbon groupinclude the same groups as those described above as the “divalenthydrocarbon group which may have a substituent” in the explanation ofthe above-described divalent linking group.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, a linearalkylene group is more preferable, a linear alkylene group having 1 to 5carbon atoms is still more preferable, and a methylene group or anethylene group is particularly preferable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group, or an alkylmethylene group ismore preferable. The alkyl group in the alkylmethylene group ispreferably a linear alkyl group having 1 to 5 carbon atoms, morepreferably a linear alkyl group having 1 to 3 carbon atoms, and mostpreferably a methyl group.

In the group represented by Formula —[Y²¹—C(═O)—O]_(m″)—Y²²—, m″represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and particularly preferably 1. In other words, it isparticularly preferable that the group represented by Formula—[Y²¹—C(═O)—O]_(m″)—Y²²— is a group represented by Formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by Formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′represents an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1. b′ represents an integer of 1 to 10, preferably an integerof 1 to 8, more preferably an integer of 1 to 5, still more preferably 1or 2, and most preferably 1.

As Ya²¹, a single bond, an ester bond [—C(═O)—O—], an ether bond (—O—),a linear or branched alkylene group, or a combination of these ispreferable.

In Formula (a2-1), La²¹ represents —O—, —COO—, —CON(R′)—, —OCO—,—CONHCO—, or —CONHCS—.

R′ represents a hydrogen atom or a methyl group.

Here, in a case where La²¹ represents —O—, Ya²¹ does not represent —CO—.

In Formula (a2-1), Ra²¹ represents a lactone-containing cyclic group, a—SO₂-containing cyclic group, or a carbonate-containing cyclic group.

Preferred examples of the lactone-containing cyclic group, the—SO₂-containing cyclic group, and the carbonate-containing cyclic groupas Ra²¹ include groups represented by Formulae (a2-r-1) to (a2-r-7),groups represented by Formulae (a5-r-1) to (a5-r-4), and groupsrepresented by Formulae (ax3-r-1) to (ax3-r-3).

Among the examples, Ra²¹ represents preferably a lactone-containingcyclic group or a —SO₂-containing cyclic group and more preferably agroup represented by Formula (a2-r-1), (a2-r-2), (a2-r-6) or (a5-r-1).Specifically, a group represented by any of chemical Formulae (r-1c-1-1)to (r-1c-1-7), (r-1c-2-1) to (r-1c-2-18), (r-1c-6-1), (r-s1-1-1), and(r-s1-1-18) is still more preferable.

The constitutional unit (a2) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (a2), theproportion of the constitutional unit (a2) in the component (A1) ispreferably in a range of 1% to 80% by mole, more preferably in a rangeof 3% to 70% by mole, still more preferably in a range of 5% to 60% bymole, and even more preferably in a range of 10% to 50% by mole withrespect to the total amount (100% by mole) of all constitutional unitsconstituting the component (A1).

In a case where the proportion of the constitutional unit (a2) isgreater than or equal to the lower limit of the above preferable range,the effect obtained by allowing the component (A1) to contain theconstitutional unit (a2) can be satisfactorily achieved. On thecontrary, in a case where the proportion of the constitutional unit (a2)is less than or equal to the upper limit of the above preferable range,the constitutional unit (a2) and other constitutional units can bebalanced, and various lithography characteristics and the pattern shapecan be improved.

In regard to constitutional unit (a3):

The component (A1) may further have a constitutional unit (a3)containing a polar group-containing aliphatic hydrocarbon group inaddition to the constitutional units (a0-1) and (a0-2) (here, aconstitutional unit corresponding to any of the above-describedconstitutional unit (a1) or (a2) is excluded).

In a case where the component (A1) includes the constitutional unit(a3), the hydrophilicity of the component (A1) is enhanced, therebycontributing to improvement of the resolution.

Examples of the polar group include a hydroxyl group, a cyano group, acarboxy group, or a hydroxyalkyl group in which some hydrogen atoms ofthe alkyl group have been substituted with fluorine atoms. Among these,a hydroxyl group is particularly preferable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) having 1 to 10 carbonatoms, and cyclic aliphatic hydrocarbon groups (cyclic groups). Thecyclic group may be a monocyclic group or a polycyclic group. Forexample, these cyclic groups can be selected appropriately from themultitude of groups that have been proposed for the resins of resistcompositions for ArF excimer lasers. The cyclic group is preferably apolycyclic group and more preferably a polycyclic group having 7 to 30carbon atoms.

Among the examples, constitutional units derived from acrylic acid esterthat include an aliphatic polycyclic group containing a hydroxyl group,cyano group, carboxy group, or a hydroxyalkyl group in which somehydrogen atoms of the alkyl group have been substituted with fluorineatoms are particularly preferable. Examples of the polycyclic groupinclude groups in which two or more hydrogen atoms have been removedfrom a bicycloalkane, tricycloalkane, tetracycloalkane or the like.Specific examples thereof include groups in which two or more hydrogenatoms have been removed from a polycycloalkane such as adamantane,norbornane, isobornane, tricyclodecane or tetracyclododecane. Amongthese polycyclic groups, groups in which two or more hydrogen atoms havebeen removed from adamantane, groups in which two or more hydrogen atomshave been removed from norbornane or groups in which two or morehydrogen atoms have been removed from tetracyclododecane are preferredindustrially.

The constitutional unit (a3) is not particularly limited as long as theconstitutional unit contains a polar group-containing aliphatichydrocarbon group, and an optional constitutional unit may be used.

The constitutional unit (a3) is a constitutional unit derived fromacrylic acid ester in which the hydrogen atom bonded to the carbon atomat the α-position may be substituted with a substituent, and aconstitutional unit containing a polar group-containing aliphatichydrocarbon group is preferable.

In a case where the hydrocarbon group in the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon grouphaving 1 to 10 carbon atoms, the constitutional unit (a3) is preferablya constitutional unit derived from hydroxyethyl ester of acrylic acid.On the other hand, in a case where the hydrocarbon group is a polycyclicgroup, a constitutional unit represented by Formula (a3-1), aconstitutional unit represented by Formula (a3-2), and a constitutionalunit represented by Formula (a3-3) shown below are preferable.

[In the formulae, R has the same definition as described above, jrepresents an integer of 1 to 3, k represents an integer of 1 to 3, t′represents an integer of 1 to 3, 1 represents an integer of 1 to 5, ands represents an integer of 1 to 3.]

In Formula (a3-1), j represents preferably 1 or 2 and more preferably 1.In a case where j represents 2, it is preferable that the hydroxylgroups is bonded to the 3rd and 5th positions of the adamantyl group. Ina case where j represents 1, it is preferable that the hydroxyl group isbonded to the 3rd position of the adamantyl group.

j represents preferably 1, and it is particularly preferable that thehydroxyl group is bonded to the 3rd position of the adamantyl group.

In Formula (a3-2), k represents preferably 1. The cyano group ispreferably bonded to the 5th or 6th position of the norbornyl group.

In Formula (a3-3), t′ represents preferably 1. l representspreferably 1. s represents preferably 1. Further, it is preferable thata 2-norbornyl group or 3-norbornyl group is bonded to the terminal ofthe carboxy group of the acrylic acid. The fluorinated alkyl alcohol ispreferably bonded to the 5th or 6th position of the norbornyl group.

The constitutional unit (a3) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (a3), theproportion of the constitutional unit (a3) in the component (A1) ispreferably in a range of 1% to 50% by mole, more preferably in a rangeof 3% to 40% by mole, still more preferably in a range of 5% to 30% bymole, and particularly preferably in a range of 10% to 30% by mole withrespect to the total amount (100% by mole) of all constitutional unitsconstituting the component (A1).

By setting the proportion of the constitutional unit (a3) to be greaterthan or equal to the lower limit, the resolution in the formation of aresist pattern is further improved. Further, by setting the proportionof the constitutional unit (a3) to be lower than or equal to the upperlimit, the constitutional unit (a3) and other constitutional units canbe balanced.

In regard to constitutional unit (a4):

The component (A1) may further have a constitutional unit (a4)containing an acid undissociable aliphatic cyclic group in addition tothe constitutional unit (a0).

In a case where the component (A1) includes the constitutional unit(a4), the dry etching resistance of the resist pattern to be formed isimproved. Further, the hydrophobicity of the component (A1) is improved.An increase in the hydrophobicity contributes to improvement of theresolution, the shape of the resist pattern, and the like particularlyin a case of a solvent developing process.

The “acid undissociable aliphatic cyclic group” in the constitutionalunit (a4) indicates a cyclic group which remains in the constitutionalunit without being dissociated even at the time of an action of an acidin a case where an acid is generated in the resist composition uponexposure (for example, an acid is generated from the constitutional unitthat generates an acid upon exposure or the component (B)).

As the constitutional unit (a4), a constitutional unit which contains anacid undissociable aliphatic cyclic group and is also derived fromacrylic acid ester is preferable. As the cyclic group, any of themultitude of conventional polycyclic groups used in the resin componentof resist compositions for ArF excimer lasers or KrF excimer lasers(preferably for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from among a tricyclodecyl group, an adamantylgroup, a tetracyclododecyl group, an isobornyl group, and a norbornylgroup is particularly preferable. These polycyclic groups may include alinear or branched alkyl group having 1 to 5 carbon atoms as asubstituent.

Specific examples of the constitutional unit (a4) include constitutionalunits represented by Formulae (a4-1) to (a4-7) shown below.

[In the formula, R^(α) has the same definition as described above.]

The constitutional unit (a4) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (a4), theproportion of the constitutional unit (a4) in the component (A1) ispreferably in a range of 1% to 40% by mole and more preferably in arange of 5% to 20% by mole with respect to the total amount (100% bymole) of all constitutional units constituting the component (A1).

By setting the proportion of the constitutional unit (a4) to be greaterthan or equal to the lower limit of the above preferable range, theeffect obtained by allowing the component (A1) to contain theconstitutional unit (a4) can be satisfactorily achieved. On thecontrary, by setting the proportion of the constitutional unit (a4) tobe less than or equal to the upper limit of the above preferable range,the constitutional unit (a4) and other constitutional units can bebalanced, and various lithography characteristics and the pattern shapecan be improved.

In regard to constitutional unit (constitutional unit (st)) derived fromstyrene or derivative thereof:

The term “styrene” is a concept including those obtained by substitutionof styrene and a hydrogen atom at the α-position of styrene with othersubstituents such as an alkyl group and a halogenated alkyl group. Here,examples of the alkyl group as the substituent include an alkyl grouphaving 1 to 5 carbon atoms, and examples of the halogenated alkyl groupas the substituent include a halogenated alkyl group having 1 to 5carbon atoms.

Examples of the “styrene derivative” include those in which the hydrogenatom at the α-position may be substituted with a substituent and thesubstituent is bonded to a benzene ring of styrene.

Further, the α-position (the carbon atom at the α-position) indicatesthe carbon atom to which the benzene ring is bonded, unless otherwisespecified.

The “constitutional unit derived from styrene” or “constitutional unitderived from a styrene derivative” indicates a constitutional unit thatis formed by the cleavage of the ethylenic double bond of styrene or astyrene derivative.

The constitutional unit (st) included in the component (A1) may be usedalone or two or more kinds thereof.

In a case where the component (A1) has the constitutional unit (st), theproportion of the constitutional unit (st) in the component (A1) ispreferably in a range of 1% to 30% by mole and more preferably in arange of 3% to 20% by mole with respect to the total amount (100% bymole) of all constitutional units constituting the component (A1).

In the resist composition of the present embodiment, the resin componentwhich is the component (A1) contains a polymer (hereinafter, alsoreferred to as a “component (A1-1)”) having the constitutional unit(a0), and the polymer may be used alone or in combination of two or morekinds thereof.

As the component (A1-1), a component that contains a copolymer havingthe constitutional unit (a0-1), the constitutional unit (a0-2), and theconstitutional unit (a10), and other constitutional units as necessaryis preferably exemplified. Such a component (A1-1), a copolymer formedof repeating structures which are the constitutional unit (a0-1), theconstitutional unit (a0-2), and the constitutional unit (a10) issuitably exemplified.

<<Component (A2)>>

In the resist composition of the present embodiment, a base materialcomponent (hereinafter, referred to as a “component (A2)”) which doesnot correspond to the component (A1) and whose solubility in adeveloping solution is changed due to the action of an acid may be usedin combination as the component (A).

The component (A2) is not particularly limited, and may be optionallyselected from those known in the related art as the base materialcomponents for a chemically amplified resist composition.

In the component (A2), a high molecular weight compound or a lowmolecular weight compound may be used alone or in combination of two ormore kinds thereof.

The proportion of the component (A1) in the component (A) is preferably50% by mass or greater, more preferably 75% by mass or greater, stillmore preferably 90% by mass or greater, and may be 100% by mass withrespect to the total mass of the component (A).

In a case where the proportion of the component (A1) is greater than orequal to the lower limit of the above-described preferable range, aresist pattern with improved lithography characteristics, such as highsensitivity, the resolution, and roughness reduction, can be reliablyformed.

In the resist composition of the present embodiment, the content of thecomponent (A) may be appropriately adjusted according to the filmthickness of a resist intended to be formed.

<Other Components>

The resist composition of the present embodiment may further containcomponents other than the component (A) in addition to theabove-described component (A). As other components, a component (B), acomponent (D), a component (E), a component (F), and a component (S)described below are exemplified.

<<Acid Generator Component (B)>>

The resist composition of the present embodiment may further contain anacid generator component (hereinafter, referred to as a “component (B)”)in addition to the component (A).

The component (B) is not particularly limited, and those which have beenproposed as an acid generator for a chemically amplified resist in therelated art can be used.

Examples of these acid generators are numerous and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate-based acid generators; diazomethane-based acid generators suchas bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate-based acidgenerators; iminosulfonate-based acid generators; and disulfone-basedacid generators. Among these examples, it is preferable to use an oniumsalt acid generator.

As the onium salt acid generator, a compound represented by Formula(b-1) (hereinafter, also referred to as “component (b-1)”), a compoundrepresented by Formula (b-2) (hereinafter, also referred to as“component (b-2)”) or a compound represented by Formula (b-3)(hereinafter, also referred to as “component (b-3)”) can be used.

[In the formulae, R¹⁰¹ and R¹⁰⁴ to R¹⁰⁸ each independently represent acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent, or a chain-like alkenyl group which mayhave a substituent, provided that R¹⁰⁴ and R¹⁰⁵ may be bonded to eachother to form a ring.

R¹⁰² represents a fluorine atom or a fluorinated alkyl group having 1 to5 carbon atoms. Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom. V¹⁰¹ to V¹⁰³ each independentlyrepresent a single bond, an alkylene group, or a fluorinated alkylenegroup. L¹⁰¹ and L¹⁰² each independently represent a single bond or anoxygen atom. L¹⁰³ to L¹⁰⁵ each independently represent a single bond,—CO— or —SO₂—. m represents an integer of 1 or greater, and M′^(m+)represents an m-valent onium cation.]

{Anion Moiety}

Anion Moiety of Component (b-1)

In Formula (b-1), R¹⁰¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent, or achain-like alkenyl group which may have a substituent.

Cyclic Group which May have Substituent:

The cyclic group is preferably a cyclic hydrocarbon group, and thecyclic hydrocarbon group may be an aromatic hydrocarbon group or analiphatic hydrocarbon group. The aliphatic hydrocarbon group indicates ahydrocarbon group that has no aromaticity. The aliphatic hydrocarbongroup may be saturated or unsaturated, but in general, the aliphatichydrocarbon group is preferably saturated.

The aromatic hydrocarbon group as R¹⁰¹ is a hydrocarbon group having anaromatic ring. The aromatic hydrocarbon group has preferably 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,particularly preferably 6 to 15, and most preferably 6 to 10. Here, thenumber of carbon atoms in a substituent is not included in the number ofcarbon atoms.

Specific examples of the aromatic ring contained in the aromatichydrocarbon group as R¹⁰¹ include benzene, fluorene, naphthalene,anthracene, phenanthrene, biphenyl, or an aromatic hetero ring in whichsome carbon atoms constituting any of these aromatic rings have beensubstituted with hetero atoms. Examples of the hetero atom in thearomatic hetero rings include an oxygen atom, a sulfur atom, and anitrogen atom.

Specific examples of the aromatic hydrocarbon group as R¹⁰¹ include agroup in which one hydrogen atom has been removed from theabove-described aromatic ring (an aryl group such as a phenyl group or anaphthyl group), and a group in which one hydrogen atom in the aromaticring has been substituted with an alkylene group (an arylalkyl groupsuch as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a2-naphthylmethyl group, 1-naphthylethyl group, or a 2-naphthylethylgroup). The alkylene group (an alkyl chain in the arylalkyl group) haspreferably 1 to 4 carbon atom, more preferably 1 or 2 carbon atoms, andparticularly preferably 1 carbon atom.

Examples of the cyclic aliphatic hydrocarbon group as R¹⁰¹ includealiphatic hydrocarbon groups containing a ring in the structure thereof.

Examples of the aliphatic hydrocarbon group containing a ring in thestructure thereof include an alicyclic hydrocarbon group (a group inwhich one hydrogen atom has been removed from an aliphatic hydrocarbonring), a group in which the alicyclic hydrocarbon group is bonded to theterminal of a linear or branched aliphatic hydrocarbon group, and agroup in which the alicyclic hydrocarbon group is interposed in a linearor branched aliphatic hydrocarbon group.

The alicyclic hydrocarbon group has preferably 3 to 20 carbon atoms andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be a polycyclic group or amonocyclic group. As the monocyclic alicyclic hydrocarbon group, a groupin which one or more hydrogen atoms have been removed from amonocycloalkane is preferable. The monocycloalkane has preferably 3 to 6carbon atoms, and specific examples thereof include cyclopentane andcyclohexane. As the polycyclic alicyclic hydrocarbon group, a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane is preferable, and the number of carbon atoms of thepolycycloalkane is preferably in a range of 7 to 30. Amongpolycycloalkanes, a polycycloalkane having a bridged ring polycyclicskeleton, such as adamantane, norbornane, isobornane, tricyclodecane, ortetracyclododecane, and a polycycloalkane having a fused ring polycyclicskeleton, such as a cyclic group having a steroid skeleton arepreferable.

Among these examples, as the cyclic aliphatic hydrocarbon group as R¹⁰¹,a group in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane is preferable, a group in which onehydrogen atom has been removed from a polycycloalkane is morepreferable, an adamantyl group or a norbornyl group is particularlypreferable, and an adamantyl group is most preferable.

The linear or branched aliphatic hydrocarbon group which may be bondedto the alicyclic hydrocarbon group has preferably 1 to 10 carbon atoms,more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbonatoms, and particularly preferably 1 to 3 carbon atoms.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄-] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferable, and specific examples thereof include variousalkylalkylene groups, for example, alkylmethylene groups such as—CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—,—C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as—CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and—C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and—CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as—CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—. As the alkyl group in thealkylalkylene group, a linear alkyl group having 1 to 5 carbon atoms ispreferable.

The cyclic hydrocarbon group as R¹⁰¹ may contain a hetero atom such as ahetero ring. Specific examples thereof include lactone-containing cyclicgroups represented by Formulae (a2-r-1) to (a2-r-7), the —SO₂-containingcyclic group represented by Formulae (a5-r-1) to (a5-r-4), and otherheterocyclic groups represented by Chemical Formulae (r-hr-1) to(r-hr-16).

Examples of the substituent for the cyclic group as R¹⁰¹ include analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxyl group, a carbonyl group, and a nitro group.

The alkyl group as the substituent is preferably an alkyl group having 1to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group,an n-butyl group, or a tert-butyl group is most preferable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group,an n-propoxy group, an iso-propoxy group, an n-butoxy group, or atert-butoxy group, and most preferably a methoxy group or an ethoxygroup.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom, and an iodine atom, and afluorine atom is preferable.

Example of the above-described halogenated alkyl group as thesubstituent includes a group in which some or all hydrogen atoms in analkyl group having 1 to 5 carbon atoms such as a methyl group, an ethylgroup, a propyl group, an n-butyl group, or a tert-butyl group have beensubstituted with the above-described halogen atoms. The carbonyl groupas the substituent is a group that substitutes a methylene group (—CH₂—)constituting the cyclic hydrocarbon group.

Chain-Like Alkyl Group which May have Substituent:

The chain-like alkyl group as R¹⁰¹ may be linear or branched.

The linear alkyl group has preferably 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbonatoms. Specific examples thereof include a methyl group, an ethyl group,a propyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decanyl group, an undecyl group,a dodecyl group, a tridecyl group, an isotridecyl group, a tetradecylgroup, a pentadecyl group, a hexadecyl group, an isohexadecyl group, aheptadecyl group, an octadecyl group, a nonadecyl group, an icosylgroup, a henicosyl group, and a docosyl group.

The branched alkyl group has preferably 3 to 20 carbon atoms, morepreferably 3 to 15, and most preferably 3 to 10. Specific examplesthereof include a 1-methylethyl group, a 1-methylpropyl group, a2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group,and a 4-methylpentyl group.

Chain-Like Alkenyl Group which May have Substituent:

Such a chain-like alkenyl group as R¹⁰¹ may be linear or branched, andthe number of carbon atoms thereof is preferably in a range of 2 to 10,more preferably in a range of 2 to 5, still more preferably in a rangeof 2 to 4, and particularly preferably 3. Examples of the linear alkenylgroup include a vinyl group, a propenyl group (an allyl group), and abutynyl group. Examples of the branched alkenyl group include a1-methylvinyl group, a 2-methylvinyl group, a 1-methylpropenyl group,and a 2-methylpropenyl group.

Among the examples, as the chain-like alkenyl group, a linear alkenylgroup is preferable, a vinyl group or a propenyl group is morepreferable, and a vinyl group is particularly preferable.

As the substituent for the chain-like alkyl group or alkenyl group asR¹⁰¹, an alkoxy group, a halogen atom, a halogenated alkyl group, ahydroxyl group, a carbonyl group, a nitro group, an amino group, acyclic group as R¹⁰¹ or the like can be used.

Among the examples, as R¹⁰¹, a cyclic group which may have a substituentis preferable, and a cyclic hydrocarbon group which may have asubstituent is more preferable. More specific preferred examples thereofinclude a phenyl group, a naphthyl group, a group in which one or morehydrogen atoms have been removed from a polycycloalkane, alactone-containing cyclic group represented by any of Formulae (a2-r-1)to (a2-r-7), and a —SO₂-containing cyclic group represented by any ofFormulae (a5-r-1) to (a5-r-4).

In Formula (b-1), Y¹⁰¹ represents a single bond or a divalent linkinggroup containing an oxygen atom.

In a case where Y¹⁰¹ represents a divalent linking group containing anoxygen atom, Y¹⁰¹ may contain an atom other than an oxygen atom.Examples of atoms other than an oxygen atom include a carbon atom, ahydrogen atom, a sulfur atom, and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an oxycarbonylgroup (—O—C(═O)—), an amide bond (—C(═O)—NH—), a carbonyl group(—C(═O)—), or a carbonate bond (—O—C(═O)—O—); and combinations of theabove-described non-hydrocarbon oxygen atom-containing linking groupswith an alkylene group. Furthermore, a sulfonyl group (—SO₂—) may belinked to the combination. Examples of divalent linking groupscontaining an oxygen atom include linking groups represented by Formulae(y-a1-1) to (y-a1-7) shown below.

[In the formulae, V′¹⁰¹ represents a single bond or an alkylene grouphaving 1 to 5 carbon atoms, and V′¹⁰² represents a divalent saturatedhydrocarbon group having 1 to 30 carbon atoms.]

The divalent saturated hydrocarbon group as V′¹⁰² is preferably analkylene group having 1 to 30 carbon atoms, more preferably an alkylenegroup having 1 to 10 carbon atoms, and still more preferably an alkylenegroup having 1 to 5 carbon atoms.

The alkylene group as V′¹⁰¹ and V′¹⁰² may be a linear alkylene group ora branched alkylene group, and a linear alkylene group is preferable.

Specific examples of the alkylene group as V′¹⁰¹ and V′¹⁰² include amethylene group [—CH₂—]; an alkylmethylene group such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, or—C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; an alkylethylene group suchas —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, or —CH(CH₂CH₃)CH₂—; atrimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; analkyltrimethylene group such as —CH(CH₃)CH₂CH₂— or —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; an alkyltetramethylene group suchas —CH(CH₃)CH₂CH₂CH₂—, —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group[—CH₂CH₂CH₂CH₂CH₂—].

Further, a part of methylene group in the alkylene group as V′¹⁰¹ andV′¹⁰² may be substituted with a divalent aliphatic cyclic group having 5to 10 carbon atoms. The aliphatic cyclic group is preferably a divalentgroup in which one hydrogen atom has been removed from the cyclicaliphatic hydrocarbon group (a monocyclic alicyclic hydrocarbon group ora polycyclic alicyclic hydrocarbon group) as R¹⁰¹ in Formula (b-1), anda cyclohexylene group, a 1,5-adamantylene group, or a 2,6-adamantylenegroup is more preferable.

Y¹⁰¹ represents preferably a divalent linking group containing an esterbond or a divalent linking group containing an ether bond and morepreferably linking groups represented by Formulae (y-a1-1) to (y-a1-5).

In Formula (b-1), V¹⁰¹ represents a single bond, an alkylene group, or afluorinated alkylene group. The alkylene group and the fluorinatedalkylene group as V¹⁰¹ preferably have 1 to 4 carbon atoms. Examples ofthe fluorinated alkylene group as V¹⁰¹ include a group in which some orall hydrogen atoms in the alkylene group as V¹⁰¹ have been substitutedwith fluorine atoms. Among these examples, as V¹⁰¹, a single bond or afluorinated alkylene group having 1 to 4 carbon atoms is preferable.

In Formula (b-1), R¹⁰² represents a fluorine atom or a fluorinated alkylgroup having 1 to 5 carbon atoms. R¹⁰² represents preferably a fluorineatom or a perfluoroalkyl group having 1 to 5 carbon atoms and morepreferably a fluorine atom.

As a specific example of the anion moiety for the component (b-1), in acase where Y¹⁰¹ represents a single bond, a fluorinated alkylsulfonateanion such as a trifluoromethanesulfonate anion or aperfluorobutanesulfonate anion can be exemplified; and in a case whereY¹⁰¹ represents a divalent linking group containing an oxygen atom,anions represented by Formulae (an-1) to (an-3) shown below can beexemplified.

[In the formulae, R″¹⁰¹ represents an aliphatic cyclic group which mayhave a substituent, a group represented by any of Formulae (r-hr-1) to(r-hr-6), or a chain-like alkyl group which may have a substituent;R″¹⁰² represents an aliphatic cyclic group which may have a substituent,a lactone-containing cyclic group represented by any of Formulae(a2-r-1) to (a2-r-7), or a —SO₂-containing cyclic group represented byany of Formulae (a5-r-1) to (a5-r-4); R″¹⁰³ represents an aromaticcyclic group which may have a substituent, an aliphatic cyclic groupwhich may have a substituent, or a chain-like alkenyl group which mayhave a substituent; each v″ independently represents an integer of 0 to3; each q″ independently represents an integer of 1 to 20; t″ representsan integer of 1 to 3; and n″ represents 0 or 1.]

As the aliphatic cyclic group as R″¹⁰¹, R″¹⁰², and R″¹⁰³ which may havea substituent, the same groups as the cyclic aliphatic hydrocarbon groupas R¹⁰¹ described above are preferable. As the substituent, the samegroups as the substituents which may substitute the cyclic aliphatichydrocarbon group as R¹⁰¹ can be exemplified.

As the aromatic cyclic group as R″¹⁰³ which may have a substituent, thesame groups as the aromatic hydrocarbon group for the cyclic hydrocarbongroup represented by R¹⁰¹ described above are preferable. As thesubstituent, the same groups as the substituents which may substitutethe aromatic hydrocarbon group as R¹⁰¹ can be exemplified.

As the chain-like alkyl group as R″¹⁰¹ which may have a substituent, thesame groups exemplified as the chain-like alkyl groups represented byR¹⁰¹ are preferable. As the chain-like alkenyl group as R″¹⁰³ which mayhave a substituent, the same groups exemplified as the chain-likealkenyl groups represented by R¹⁰¹ are preferable.

Anion Moiety of Component (b-2)

In Formula (b-2), R¹⁰⁴ and R¹⁰⁵ each independently represent a cyclicgroup which may have a substituent, a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and has the same definition as that for R¹⁰¹ in Formula(b-1). R¹⁰⁴ and R¹⁰⁵ may be bonded to each other to form a ring.

As R¹⁰⁴ and R¹⁰⁵, a chain-like alkyl group which may have a substituentis preferable, and a linear or branched alkyl group or a linear orbranched fluorinated alkyl group is more preferable.

The chain-like alkyl group has preferably 1 to 10 carbon atoms, morepreferably 1 to 7 carbon atoms, and still more preferably 1 to 3 carbonatoms. It is preferable that the number of carbon atoms in thechain-like alkyl group as R¹⁰⁴ and R¹⁰⁵ is small because the solubilityin a solvent for a resist is also excellent in the range of the numberof carbon atoms. Further, in the chain-like alkyl group as R¹⁰⁴ andR¹⁰⁵, it is preferable that the number of hydrogen atoms substitutedwith fluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beams is improved.

The proportion of fluorine atoms in the chain-like alkyl group, that is,the fluorination ratio is preferably in a range of 70% to 100% and morepreferably in a range of 90% to 100%, and it is most preferable that thechain-like alkyl group is a perfluoroalkyl group in which all hydrogenatoms are substituted with fluorine atoms.

In Formula (b-2), V¹⁰² and V¹⁰³ each independently represent a singlebond, an alkylene group, or a fluorinated alkylene group, and has thesame definition as that for V¹⁰¹ in Formula (b-1).

In Formula (b-2), L¹⁰¹ and L¹⁰² each independently represent a singlebond or an oxygen atom.

Anion Moiety of Component (b-3)

In Formula (b-3), R¹⁰⁶ to R¹⁰⁸ each independently represent a cyclicgroup which may have a substituent or a chain-like alkyl group which mayhave a substituent or a chain-like alkenyl group which may have asubstituent, and has the same definition as that for R¹⁰¹ in Formula(b-1).

L¹⁰³ to L¹⁰⁵ each independently represent a single bond, —CO—, or —SO₂—.

{Cation Moiety}

In Formulae (b-1), (b-2), and (b-3), m represents an integer of 1 orgreater, M′^(m+) represents an m-valent onium cation and preferably asulfonium cation or an iodonium cation. Further, an organic cationrepresented by any of Formulae (ca-1) to (ca-5) is particularlypreferable.

[In the formulae, R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² each independentlyrepresent an aryl group, an alkyl group, or an alkenyl group which mayhave a substituent, provided that R²⁰¹ to R²⁰³, R²⁰⁶ and R²⁰⁷, and R²¹¹and R²¹² may be bonded to each other to form a ring with the sulfur atomin the formula; R²⁰⁸ and R²⁰⁹ each independently represent a hydrogenatom or an alkyl group having 1 to 5 carbon atoms; R²¹⁰ represents anaryl group which may have a substituent, an alkyl group which may have asubstituent, an alkenyl group which may have a substituent, or a—SO₂-containing cyclic group which may have a substituent; L²⁰¹represents —C(═O)— or —C(═O)—O—; Y²⁰¹ each independently represent anarylene group, an alkylene group, or an alkenylene group; x represents 1or 2; and W²⁰¹ represents a (x+1)-valent linking group.]

Examples of the aryl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² include anunsubstituted aryl group having 6 to 20 carbon atoms, and a phenyl groupor a naphthyl group is preferable.

The alkyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² is a chain-like orcyclic alkyl group, and the number of carbon atoms thereof is preferablyin a range of 1 to 30.

The alkenyl group as R²⁰¹ to R²⁰⁷, R²¹¹, and R²¹² preferably has 2 to 10carbon atoms.

Examples of the substituent which R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² may haveinclude an alkyl group, a halogen atom, a halogenated alkyl group, acarbonyl group, a cyano group, an amino group, an aryl group, and groupsrepresented by Formulae (ca-r-1) to (ca-r-7) shown below.

[In the formulae, each R′²⁰¹ independently represents a hydrogen atom, acyclic group which may have a substituent, a chain-like alkyl groupwhich may have a substituent, or a chain-like alkenyl group which mayhave a substituent.]

As the cyclic group which may have a substituent, the chain-like alkylgroup which may have a substituent, and the chain-like alkenyl groupwhich may have a substituent as R′²⁰¹, the same groups as thosedescribed above as R¹⁰¹ in Formula (b-1) can be exemplified. As thecyclic group which may have a substituent or a chain-like alkyl groupwhich may have a substituent, the same groups as those described abovefor the acid dissociable group represented by Formula (a1-r-2) can beexemplified.

In a case where R²⁰¹ to R²⁰³, R²⁰⁶, R²⁰⁷, R²¹¹, and R²¹² are bonded toone another to form a ring with a sulfur atom in the formula, thesegroups may be bonded to one another via a hetero atom such as a sulfuratom, an oxygen atom or a nitrogen atom, or a functional group such as acarbonyl group, —SO—, —SO₂—, —SO₃—, —COO—, —CONH— or —N(R_(N))— (here,R_(N) represents an alkyl group having 1 to 5 carbon atoms). As a ringto be formed, a ring containing the sulfur atom in the formula in theskeleton thereof is preferably a 3- to 10-membered ring and mostpreferably a 5- to 7-membered ring, including the sulfur atom. Specificexamples of the ring to be formed include a thiophene ring, a thiazolering, a benzothiophene ring, a thianthrene ring, a benzothiophene ring,a dibenzothiophene ring, a 9H-thioxanthene ring, a thioxanthone ring, aphenoxathiin ring, a tetrahydrothiophenium ring, and atetrahydrothiopyranium ring.

R²⁰⁸ and R²⁰⁹ each independently represent a hydrogen atom or an alkylgroup having 1 to 5 carbon atoms and preferably a hydrogen atom or analkyl group having 1 to 3 carbon atoms. In a case where R²⁰⁸ and R²⁰⁹each represents an alkyl group, R²⁰⁸ and R²⁰⁹ may be mutually bonded toform a ring.

R²¹⁰ represents an aryl group which may have a substituent, an alkylgroup which may have a substituent, an alkenyl group which may have asubstituent, or a —SO₂-containing cyclic group which may have asubstituent.

Examples of the aryl group as R²¹⁰ include an unsubstituted aryl grouphaving 6 to 20 carbon atoms, and a phenyl group or a naphthyl group ispreferable.

As the alkyl group as R²¹⁰, a chain-like or cyclic alkyl group having 1to 30 carbon atoms is preferable.

The alkenyl group as R²¹⁰ preferably has 2 to 10 carbon atoms.

As the —SO₂-containing cyclic group as R²¹⁰ which may have asubstituent, the same groups as the —SO₂-containing cyclic grouprepresented by Formulae (a5-r-1) to (a5-r-4) are exemplified. Amongthese, a “—SO₂-containing polycyclic group” is preferable, and a grouprepresented by Formula (a5-r-1) is more preferable.

In Formulae (ca-4) and (ca-5), each Y²⁰¹ independently represents anarylene group, an alkylene group, or an alkenylene group.

Examples of the arylene group as Y²⁰¹ include groups in which onehydrogen atom has been removed from an aryl group exemplified as thearomatic hydrocarbon group represented by R¹⁰¹ in Formula (b-1).

Examples of the alkylene group and alkenylene group as Y²⁰¹ includegroups in which one hydrogen atom has been removed from the chain-likealkyl group or the chain-like alkenyl group as R¹⁰¹ in Formula (b-1).

In Formulae (ca-4) and (ca-5), x represents 1 or 2.

W²⁰¹ represents a (v+1)-valent linking group, that is, a divalent ortrivalent linking group.

As the divalent linking group represented by W²⁰¹, a divalenthydrocarbon group which may have a substituent is preferable, and asexamples thereof, the same divalent hydrocarbon groups (which may have asubstituent) as those described above represented by Ya²¹ in Formula(a2-1) can be exemplified. The divalent linking group as W²⁰¹ may belinear, branched or cyclic, and cyclic is more preferable. Among these,an arylene group having two carbonyl groups, each bonded to the terminalthereof is preferable. Examples of the arylene group include a phenylenegroup, and a naphthylene group, and a phenylene group is particularlypreferable.

As the trivalent linking group as W²⁰¹, a group in which one hydrogenatom has been removed from the above-described divalent linking group asW²⁰¹ and a group in which the divalent linking group has been bonded toanother divalent linking group can be exemplified. The trivalent linkinggroup as W²⁰¹ is preferably a group in which two carbonyl groups arebonded to an arylene group.

Specific suitable examples of the cation represented by Formula (ca-1)include cations represented by Formulae (ca-1-1) to (ca-1-72) shownbelow.

[In the formulae, g1, g2 and g3 represent a repeating number, g1represents an integer of 1 to 5, g2 represents an integer of 0 to 20,and g3 represents an integer of 0 to 20.]

[In the formulae, R″²⁰¹ represents a hydrogen atom or a substituent, andas the substituent, the same groups as those described above forsubstituting R²⁰¹ to R²⁰⁷ and R²¹⁰ to R²¹² can be exemplified.]

Specific examples of suitable cations represented by Formula (ca-2)include a dihphenyliodonium cation and a bis(4-tert-butylphenyl)iodoniumcation.

Specific examples of suitable cations represented by Formula (ca-3)include cations represented by Formulae (ca-3-1) to (ca-3-6) shownbelow.

Specific examples of suitable cations represented by Formula (ca-4)include cations represented by Formulae (ca-4-1) and (ca-4-2) shownbelow.

Further, as the cation represented by Formula (ca-5), cationsrepresented by Formulae (ca-5-1) to (ca-5-3) are also preferable.

Among the examples, as the cation moiety [(M^(m+))_(1/m)], a cationrepresented by Formula (ca-1) is preferable, and a cation represented byany of Formulae (ca-1-1) to (ca-1-72) is more preferable.

In the component (B), the above-described acid generator may be usedalone or in combination of two or more kinds thereof.

In a case where the resist composition contains the component (B), thecontent of the component (B) is preferably in a range of 5 to 50 partsby mass, more preferably in a range of 10 to 40 parts by mass, and stillmore preferably in a range of 10 to 30 parts by mass with respect to 100parts by mass of the component (A).

In a case where the content of the component (B) is in theabove-described range, pattern formation can be satisfactorilyperformed. Further, it is preferable that the content thereof is in theabove-described range because a uniform solution is easily obtained atthe time of dissolving each component of the resist composition in anorganic solvent, and the storage stability of the resist compositionbecomes excellent.

<<Acid Diffusion Control Agent Component (D)>>

The resist composition of the present embodiment may further contain anacid diffusion control agent component (hereinafter, referred to as a“component (D)”) in addition to the component (A) or the component (A)and the component (B). The component (D) acts as a quencher (an aciddiffusion control agent) which traps the acid generated in the resistcomposition upon exposure.

The component (D) may be a photodecomposable base (D1) (hereinafter,referred to as “component (D1)”) which is decomposed upon exposure andthen loses the acid diffusion controllability or a nitrogen-containingorganic compound (D2) (hereinafter, referred to as “component (D2)”)which does not correspond to the component (D1).

In Regard to Component (D1)

In a case where a resist composition containing the component (D1) isobtained, the contrast between exposed portions and unexposed portionsof the resist film can be improved at the time of formation of a resistpattern.

The component (D1) is not particularly limited as long as decompositionis made upon exposure so that the acid diffusion controllability islost, and one or more compounds selected from the group consisting of acompound represented by Formula (d1-1) (hereinafter, referred to as a“component (d1-1)”), a compound represented by Formula (d1-2)(hereinafter, referred to as “component (d1-2)”), and a compoundrepresented by Formula (d1-3) (hereinafter, referred to as “component(d1-3)”) are preferable.

At exposed portions of the resist film, the components (d1-1) to (d1-3)are decomposed and then lose the acid diffusion controllability(basicity), and therefore the components (d1-1) to (d1-3) cannot act asa quencher, whereas at unexposed portions, the components (d1-1) to(d1-3) acts as a quencher.

[In the formulae, Rd¹ to Rd⁴ represent a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, provided that,the carbon atom adjacent to the sulfur atom in the Rd² in Formula (d1-2)has no fluorine atom bonded thereto; Yd¹ represents a single bond or adivalent linking group; m represents an integer of 1 or greater; andeach M^(m+) independently represents an m-valent organic cation.]

{Component (d1-1)}

Anion Moiety

In Formula (d1-1), Rd¹ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and examplesthereof are the same as those described above as R¹⁰¹ in Formula (b-1).

Among these, as the group as Rd¹, an aromatic hydrocarbon group whichmay have a substituent, an aliphatic cyclic group which may have asubstituent and a chain-like alkyl group which may have a substituentare preferable. Examples of the substituent for these groups include ahydroxyl group, an oxo group, an alkyl group, an aryl group, a fluorineatom, a fluorinated alkyl group, a lactone-containing cyclic grouprepresented by any of Formulae (a2-r-1) to (a2-r-7), an ether bond, anester bond, and a combination thereof. In a case where an ether bond oran ester bond is included as the substituent, the substituent may bebonded via an alkylene group, and a linking group represented by any ofFormulae (y-a1-1) to (y-a1-5) is preferable as the substituent.

The aromatic hydrocarbon group is preferably a phenyl group or anaphthyl group.

Examples of the aliphatic cyclic group include groups in which one ormore hydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane.

The chain-like alkyl group preferably has 1 to 10 carbon atoms, andspecific examples thereof include a linear alkyl group such as a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, or a decylgroup, and a branched alkyl group such as a 1-methylethyl group, a1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a3-methylpentyl group, or a 4-methylpentyl group.

In a case where the chain-like alkyl group is a fluorinated alkyl grouphaving a fluorine atom or a fluorinated alkyl group as a substituent,the fluorinated alkyl group has preferably 1 to 11 carbon atoms, morepreferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbonatoms. The fluorinated alkyl group may contain an atom other thanfluorine. Examples of the atom other than fluorine include an oxygenatom, a sulfur atom, and a nitrogen atom.

As Rd¹, a fluorinated alkyl group in which some or all hydrogen atomsconstituting a linear alkyl group have been substituted with fluorineatom(s) is preferable, and a fluorinated alkyl group in which all of thehydrogen atoms constituting a linear alkyl group have been substitutedwith fluorine atoms (a linear perfluoroalkyl group) is particularlypreferable.

Specific examples of preferable anion moieties for the component (d1-1)are shown below.

Cation Moiety

In Formula (d1-1), M^(m+) represents an m-valent organic cation.

As the organic cation as M^(m+,) the same cations as those representedby Formulae (ca-1) to (ca-5) are suitably exemplified, a cationrepresented by the above-described Formulae (ca-1) is more preferable,and cations represented Formulae (ca-1-1) to (ca-1-72) are still morepreferable.

The component (d1-1) may be used alone or in combination of two or morekinds thereof.

{Component (d1-2)}

Anion Moiety

In Formula (d1-2), Rd² represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent, or achain-like alkenyl group which may have a substituent, and the samegroups as those described above as R¹⁰¹ in Formula (b-1) areexemplified.

Here, the carbon atom adjacent to the S atom in Rd² has no fluorine atombonded thereto (the carbon atom adjacent to the sulfur atom in Rd² isnot substituted with a fluorine atom). As a result, the anion of thecomponent (d1-2) becomes an appropriately weak acid anion, therebyimproving the quenching ability of the component (D).

As Rd², a chain-like alkyl group which may have a substituent or analiphatic cyclic group which may have a substituent is preferable. Thechain-like alkyl group has preferably 1 to 10 carbon atoms and morepreferably 3 to 10 carbon atoms. As the aliphatic cyclic group, a groupin which one or more hydrogen atoms have been removed from adamantane,norbornane, isobornane, tricyclodecane, or tetracyclododecane (which mayhave a substituent) and a group in which one or more hydrogen atoms havebeen removed from camphor are more preferable.

The hydrocarbon group as Rd² may have a substituent. As the substituent,the same groups as the substituents which may be included in thehydrocarbon group (such as an aromatic hydrocarbon group, an aliphaticcyclic group, or a chain-like alkyl group) as Rd¹ in Formula (d1-1) canbe exemplified.

Specific examples of preferable anion moieties for the component (d1-2)are shown below.

Cation Moiety

In Formula (d1-2), M^(m+) represents an m-valent organic cation, and hasthe same definition as that for M^(m+) in the above-described Formula(d1-1).

The component (d1-2) may be used alone or in combination of two or morekinds thereof.

{Component (d1-3)}

Anion Moiety

In Formula (d1-3), Rd³ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent, or achain-like alkenyl group which may have a substituent, and the samegroups as those described above as R¹⁰¹ in Formula (b-1) areexemplified, and a cyclic group containing a fluorine atom, a chain-likealkyl group, or a chain-like alkenyl group is preferable. Among these, afluorinated alkyl group is preferable, and the same fluorinated alkylgroups as those described above as Rd¹ are more preferable.

In Formula (d1-3), Rd⁴ represents a cyclic group which may have asubstituent, a chain-like alkyl group which may have a substituent or achain-like alkenyl group which may have a substituent, and the samegroups as those described above as R¹⁰¹ in Formula (b-1) areexemplified.

Among these, an alkyl group which may have substituent, an alkoxy groupwhich may have substituent, an alkenyl group which may have substituent,or a cyclic group which may have substituent is preferable.

The alkyl group as Rd⁴ is preferably a linear or branched alkyl grouphaving 1 to 5 carbon atoms, and specific examples thereof include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, and a neopentyl group. Some hydrogen atoms in the alkylgroup as Rd⁴ may be substituted with a hydroxyl group, a cyano group, orthe like.

The alkoxy group as Rd⁴ is preferably an alkoxy group having 1 to 5carbon atoms, and specific examples thereof include a methoxy group, anethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxygroup, and a tert-butoxy group. Among these, a methoxy group and anethoxy group are preferable.

As the alkenyl group as Rd⁴, the same groups as those described above asR¹⁰¹ in Formula (b-1) can be exemplified, and a vinyl group, a propenylgroup (an allyl group), a 1-methylpropenyl group, and a 2-methylpropenylgroup are preferable. These groups may have an alkyl group having 1 to 5carbon atoms or a halogenated alkyl group having 1 to 5 carbon atoms asa substituent.

As the cyclic group as Rd⁴, the same groups as those described above asR¹⁰¹ in Formula (b-1) can be exemplified. Among these, as the cyclicgroup, an alicyclic group in which one or more hydrogen atoms have beenremoved from a cycloalkane such as cyclopentane, cyclohexane,adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecaneor an aromatic group such as a phenyl group or a naphthyl group ispreferable. In a case where Rd⁴ represents an alicyclic group, theresist composition can be satisfactorily dissolved in an organicsolvent, thereby improving the lithography characteristics. Further, ina case where Rd⁴ represents an aromatic group, the resist compositionexhibits an excellent photoabsorption efficiency in a lithographyprocess using EUV or the like as the exposure light source, therebyresulting in the improvement of the sensitivity and the lithographycharacteristics.

In Formula (d1-3), Yd¹ represents a single bond or a divalent linkinggroup.

The divalent linking group as Yd¹ is not particularly limited, andexamples thereof include a divalent hydrocarbon group (an aliphatichydrocarbon group or an aromatic hydrocarbon group) which may have asubstituent and a divalent linking group containing a hetero atom. Thedivalent linking groups are the same as described above as the divalenthydrocarbon group which may have a substituent and the divalent linkinggroup containing a hetero atom explained above as the divalent linkinggroup as Ya²¹ in Formula (a2-1).

As Yd¹, a carbonyl group, an ester bond, an amide bond, an alkylenegroup, or a combination of these is preferable. As the alkylene group, alinear or branched alkylene group is more preferable, and a methylenegroup or an ethylene group is still more preferable.

Specific examples of preferable anion moieties for the component (d1-3)are shown below.

Cation Moiety

In Formula (d1-3), M^(m+) represents an m-valent organic cation, and hasthe same definition as that for M^(m+) in Formula (d1-1).

The component (d1-3) may be used alone or in combination of two or morekinds thereof.

As the component (D1), only one of the above-described components (d1-1)to (d1-3) or a combination of two or more kinds thereof may be used.

In a case where the resist composition contains the component (D1), thecontent of the component (D1) is preferably in a range of 0.5 to 10parts by mass, more preferably in a range of 0.5 to 8 parts by mass, andstill more preferably in a range of 1 to 8 parts by mass with respect to100 parts by mass of the component (A).

In a case where the content of the component (D1) is greater than orequal to the preferable lower limit, excellent lithographycharacteristics and an excellent resist pattern shape can be morereliably obtained. Further, in a case where the content thereof is lessthan or equal to the upper limit thereof, the sensitivity can bemaintained satisfactorily, and through-put also becomes excellent.

Method of Producing Component (D1):

The production methods of the components (d-1) and (d-2) are notparticularly limited, and the components (d1-1) and (d1-2) can beproduced by known methods.

Further, the method of producing the component (d1-3) is notparticularly limited, and the component (d1-3) can be produced in thesame manner as disclosed in United States Patent Application,Publication No. 2012-0149916.

Component (D2)

The resist composition may contain a nitrogen-containing organiccompound component (hereinafter, referred to as a “component (D2)”) thatdoes not correspond to the component (D1) as the acid diffusion controlagent component.

The component (D2) is not particularly limited, as long as it acts as anacid diffusion control agent and does not correspond to the component(D1). As the component (D2), any of the conventionally known compoundsmay be optionally used. Among these, an aliphatic amine is preferable,and a secondary aliphatic amine or tertiary aliphatic amine isparticularly preferable.

An aliphatic amine is an amine having one or more aliphatic groups, andthe aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group having 12 or less carbon atoms (alkylamines oralkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine and tri-n-octylamine areparticularly preferable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidineand piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines includetris(2-methoxymethoxyethyl)amine, tris {2-(2-methoxyethoxy)ethyl}amine,tris {2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris {2-(1-ethoxyethoxy)ethyl}amine,tris {2-(1-ethoxypropoxy)ethyl}amine,tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine and triethanolaminetriacetate, and triethanolamine triacetate is preferable.

Further, as the component (D2), an aromatic amine may be used.

Examples of aromatic amines include 4-dimethylaminopyridine, pyrrole,indole, pyrazole, imidazole and derivatives thereof as well astribenzylamine, 2,6-diisopropylaniline andN-tert-butoxycarbonylpyrrolidine.

The component (D2) may be used alone or in combination of two or morekinds thereof.

In a case where the resist composition contains the component (D2), thecontent of the component (D2) is typically in a range of 0.01 to 5 partsby mass with respect to 100 parts by mass of the component (A). In acase where the content thereof is in the above-described range, theshape of the resist pattern and the post exposure temporal stability areimproved.

<<At Least One Compound (E) Selected from Group Consisting of OrganicCarboxylic Acids, Phosphorus Oxo Acids, and Derivatives Thereof>>

For the purpose of preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure temporalstability, the resist composition of the present embodiment may containat least one compound (E) (hereinafter referred to as the component (E))selected from the group consisting of an organic carboxylic acid, or aphosphorus oxo acid and a derivative thereof.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid, and phosphinic acid. Among these, phosphonic acid is particularlypreferable.

Examples of phosphorus oxo acid derivatives include esters in which ahydrogen atom in the above-described oxo acids is substituted with ahydrocarbon group. Examples of the hydrocarbon group include an alkylgroup having 1 to 5 carbon atoms and an aryl group having 6 to 15 carbonatoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate, and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid estersand phenylphosphinic acid.

The component (E) may be used alone or in combination of two or morekinds thereof.

In a case where the resist composition contains the component (E), thecontent of the component (E) is typically in a range of 0.01 to 5 partsby mass, with respect to 100 parts by mass of the component (A).

<<Fluorine Additive Component (F)>>

In the present embodiment, the resist composition may further include afluorine additive (hereinafter, referred to as “component (F)”) forimparting water repellency to the resist film.

As the component (F), a fluorine-containing polymeric compound describedin Japanese Unexamined Patent Application, First Publication No.2010-002870, Japanese Unexamined Patent Application, First PublicationNo. 2010-032994, Japanese Unexamined Patent Application, FirstPublication No. 2010-277043, Japanese Unexamined Patent Application,First Publication No. 2011-13569, and Japanese Unexamined PatentApplication, First Publication No. 2011-128226 can be exemplified.

Specific examples of the component (F) include polymers having aconstitutional unit (f1) represented by Formula (f1-1) shown below. Asthe polymer, a polymer (homopolymer) consisting of a constitutional unit(f1) represented by Formula (f1-1) shown below; a copolymer of theconstitutional unit (f1) and the above-described constitutional unit(a1) containing an acid decomposable group whose polarity is increaseddue to the action of an acid; and a copolymer of the constitutional unit(f1), a constitutional unit derived from acrylic acid or methacrylicacid and the above-described constitutional unit (a1) are preferable.Preferred examples of the constitutional unit (a1) to be copolymerizedwith the constitutional unit (f1) include a constitutional unit derivedfrom 1-ethyl-1-cyclooctyl (meth)acrylate and a constitutional unitderived from 1-methyl-1-adamantyl (meth)acrylate.

[In the formula, R has the same definition as described above; Rf¹⁰² andRf¹⁰³ each independently represent a hydrogen atom, a halogen atom, analkyl group having 1 to 5 carbon atoms, or a halogenated alkyl grouphaving 1 to 5 carbon atoms, provided that Rf¹⁰² and Rf¹⁰³ may be thesame as or different from each other; nf¹ represents an integer of 1 to5; and Rf¹⁰¹ represents an organic group containing a fluorine atom.]

In Formula (f1-1), R bonded to the carbon atom at the α-position has thesame definition as described above. As R, a hydrogen atom or a methylgroup is preferable.

In Formula (f1-1), examples of the halogen atom as Rf¹⁰² and Rf¹⁰³include a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom, and a fluorine atom is particularly preferable. Examples of thealkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³ include thosedescribed above as the alkyl group having 1 to 5 carbon atoms as R, anda methyl group or an ethyl group is preferable. Specific examples of thehalogenated alkyl group having 1 to 5 carbon atoms as Rf¹⁰² and Rf¹⁰³include groups in which some or all hydrogen atoms of theabove-described alkyl groups of 1 to 5 carbon atoms have beensubstituted with halogen atoms.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom, and an iodine atom, and a fluorine atom is particularlypreferable. Among these examples, as Rf¹⁰² and Rf¹⁰³, a hydrogen atom, afluorine atom, or an alkyl group having 1 to 5 carbon atoms ispreferable, and a hydrogen atom, a fluorine atom, a methyl group, or anethyl group is more preferable.

In Formula (f1-1), nf¹ represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably an integer of 1 or 2.

In Formula (f1-1), Rf¹⁰¹ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear,branched, or cyclic, and has preferably 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, and particularly preferably 1 to 10carbon atoms.

It is preferable that the hydrocarbon group having a fluorine atom has25% or more of the hydrogen atoms in the hydrocarbon group fluorinated,more preferably 50% or greater, and particularly preferably 60% orgreater from the viewpoint of improving the hydrophobicity of the resistfilm during immersion exposure.

Among these, as Rf¹⁰¹, a fluorinated hydrocarbon group having 1 to 6carbon atoms is preferable, and a trifluoromethyl group, —CH₂—CF₃,—CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ aremost preferable.

The weight average molecular weight (Mw) (in terms of polystyrenedetermined by gel permeation chromatography) of the component (F) ispreferably in a range of 1,000 to 50,000, more preferably in a range of5,000 to 40,000, and most preferably in a range of 10,000 to 30,000. Ina case where the weight average molecular weight is less than or equalto the upper limit of the above-described range, the resist compositionexhibits a satisfactory solubility in a solvent for a resist enough tobe used as a resist. On the other hand, in a case where the weightaverage molecular weight is greater than or equal to the lower limit ofthe above-described range, dry etching resistance and thecross-sectional shape of the resist pattern become excellent.

Further, the dispersity (Mw/Mn) of the component (F) is preferably in arange of 1.0 to 5.0, more preferably in a range of 1.0 to 3.0, and mostpreferably in a range of 1.2 to 2.5.

The component (F) may be used alone or in combination of two or morekinds thereof.

In a case where the resist composition contains the component (F), thecontent of the component (F) is typically in a range of 0.5 to 10 partsby mass, with respect to 100 parts by mass of the component (A).

As desired, other miscible additives can also be added to the resistcomposition of the present invention. The resist composition may containmiscible additives such as additive resins, dissolution inhibitors,plasticizers, stabilizers, colorants, halation prevention agents, anddyes for improving the performance of the resist film, as appropriate.

<<Organic Solvent Component (S)>>

The resist composition of the present embodiment may be produced bydissolving the resist materials in an organic solvent (hereinafter,referred to as a “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to be used to obtain a uniform solution, andoptional organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist composition and then used.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (such as monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; aromatic organic solventssuch as anisole, ethylbenzylether, cresylmethylether, diphenylether,dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene; and dimethylsulfoxide (DMSO).

The component (S) may be used alone or in the form of a mixed solvent oftwo or more kinds thereof.

Among these, PGMEA, PGME, γ-butyrolactone, EL and cyclohexanone arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (mass ratio)of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1 and more preferably in a rangeof 2:8 to 8:2.

More specifically, in a case where EL or cyclohexanone is mixed as thepolar solvent, the PGMEA:EL or cyclohexanone mass ratio is preferably ina range of 1:9 to 9:1 and more preferably in a range of 2:8 to 8:2.Alternatively, in a case where PGME is mixed as the polar solvent, thePGMEA:PGME mass ratio is preferably in a range of 1:9 to 9:1, morepreferably in a range of 2:8 to 8:2, and still more preferably in arange of 3:7 to 7:3. Furthermore, a mixed solvent of PGMEA, PGME andcyclohexanone is also preferable.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mass ratio(former:latter) of such a mixed solvent is preferably in a range of70:30 to 95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate. In general, the component (S) is usedin an amount such that the solid content of the resist compositionbecomes in the range of 1% to 20% by mass and preferably in a range of2% to 15% by mass.

In the resist composition of the present embodiment, a constitutionalunit having a specific structure, that is, a resin component (A1) havinga constitutional unit (a0-1) represented by Formula (a0-1) and aconstitutional unit (a0-2) represented by Formula (a0-2) is employed asdescribed above.

The constitutional unit (a0-1) contains an acid dissociable grouprepresented by Formula (a01-r-1) or (a01-r-2). The acid dissociablegroup represented by Formula (a01-r-1) or (a01-r-2) has a smaller volumethan that of the acid dissociable group containing a polycyclic group.Therefore, it is speculated that the constitutional unit (a0-1)increases the solubility of the resin component (A1) and contributes toreduction of the roughness of a resist pattern.

Meanwhile, the constitutional unit (a0-2) contains an acid dissociablegroup represented by Formula (a02-r-1). The acid dissociable grouprepresented by Formula (a02-r-1) contains an aromatic hydrocarbon group.

Therefore, a carbocation generated at the time of dissociation of theacid dissociable group represented by Formula (a02-r-1) has highstability. Accordingly, it is speculated that the acid dissociationproperty of the constitutional unit (a0-2) is improved and theconstitutional unit (a0-2) contributes to improvement of the resolution.

In the present invention, it is speculated that a resist composition inwhich various lithography characteristics are balanced satisfactorilyand the resolution and the roughness are improved can be obtained byusing the constitutional unit (a0-1) and the constitutional unit (a0-2)in combination.

(Method of Forming a Resist Pattern)

The method of forming a resist pattern according to the presentembodiment includes a step of forming a resist film on a support usingthe resist composition described above; a step of exposing the resistfilm; and a step of developing the exposed resist film to form a resistpattern.

According to the embodiment of the method of forming a resist pattern, amethod for forming a resist pattern by performing processes as describedbelow is exemplified.

First, a resist composition of the according to the embodiment isapplied to a support using a spinner or the like, and a bake treatment(post applied bake (PAB)) is conducted at a temperature of 80 to 150° C.for 40 to 120 seconds and preferably 60 to 90 seconds, to form a resistfilm.

Following selective exposure of the thus formed resist film, by exposurethrough a mask having a predetermined pattern formed thereon (maskpattern) using an exposure apparatus such as an ArF exposure apparatus,an electron beam lithography apparatus, or an EUV exposure apparatus, orby patterning via direct irradiation with an electron beam without usinga mask pattern, baking treatment (post exposure baking (PEB)) isconducted under temperature conditions of 80 to 150° C. for 40 to 120seconds, and preferably 60 to 90 seconds.

Next, the resist film is subjected to a developing treatment. Thedeveloping treatment is conducted using an alkali developing solution ina case of an alkali developing process, and a developing solutioncontaining an organic solvent (organic developing solution) in a case ofa solvent developing process.

After the developing treatment, it is preferable to conduct a rinsetreatment. The rinse treatment is preferably conducted using pure waterin a case of an alkali developing process, and a rinse solutioncontaining an organic solvent in a case of a solvent developing process.

In a case of a solvent developing process, after the developingtreatment or the rinsing, the developing solution or the rinse liquidremaining on the pattern can be removed by a treatment using asupercritical fluid.

After the developing treatment or the rinse treatment, drying isconducted. As desired, bake treatment (post bake) can be conductedfollowing the developing.

In this manner, a resist pattern can be formed.

The support is not specifically limited and a conventionally knownsupport can be used. For example, substrates for electronic components,and such substrates having wiring patterns formed thereon can be used.Specific examples of the material of the substrate include metals suchas silicon wafer, copper, chromium, iron, and aluminum; and glass.Suitable materials for the wiring pattern include copper, aluminum,nickel, and gold.

Further, as the support, any one of the above-described supportsprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as an ArF excimerlaser, a KrF excimer laser, an F₂ excimer laser, extreme ultravioletrays (EUV), vacuum ultraviolet rays (VUV), electron beams (EB), X-rays,and soft X-rays. The resist composition of the present invention isuseful for a KrF excimer laser, an ArF excimer laser, EB, and EUV, andparticularly useful for an ArF excimer laser, EB, and EUV.

The exposure of the resist film can be a general exposure (dry exposure)conducted in air or an inert gas such as nitrogen, or immersion exposure(immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long as it satisfies the above-describedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents, and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, and the boiling point ispreferably in a range of 70° to 180° C. and more preferably in a rangeof 80° to 160° C. A fluorine-based inert liquid having a boiling pointin the above-described range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly preferable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point of 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point of 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

As an example of the alkali developing solution used in an alkalideveloping process, a 0.1 to 10 mass % aqueous solution oftetramethylammonium hydroxide (TMAH) can be exemplified.

As the organic solvent contained in the organic developing solution usedin a solvent developing process, any of the conventional organicsolvents can be used which are capable of dissolving the component (A)(prior to exposure). Specific examples of the organic solvent includepolar solvents such as ketone solvents, ester solvents, alcoholsolvents, nitrile solvents, amide solvents and ether solvents, andhydrocarbon solvents.

A ketone solvent is an organic solvent containing C—C(═O)—C in thestructure thereof. An ester solvent is an organic solvent containingC—C(═O)—O—C in the structure thereof. An alcohol solvent is an organicsolvent containing an alcoholic hydroxyl group in the structure thereof.An “alcoholic hydroxyl group” indicates a hydroxyl group bonded to acarbon atom of an aliphatic hydrocarbon group. A nitrile solvent is anorganic solvent containing a nitrile group in the structure thereof. Anamide solvent is an organic solvent containing an amide group in thestructure thereof. An ether solvent is an organic solvent containingC—O—C in the structure thereof.

Some organic solvents have a plurality of the functional groups whichcharacterizes the above-described solvents in the structure thereof. Insuch a case, the organic solvent can be classified as any type of thesolvent having the characteristic functional group. For example,diethylene glycol monomethylether can be classified as an alcoholsolvent or an ether solvent.

A hydrocarbon solvent consists of a hydrocarbon which may behalogenated, and does not have any substituent other than a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

As the organic solvent contained in the organic developing solution,among these, a polar solvent is preferable, and ketone solvents, estersolvents, and nitrile solvents are preferable.

Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone,2-nonanone, acetone, 4-heptanone, 1-hexanone, 2-hexanone, diisobutylketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethylketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone,diacetonylalcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone,isophorone, propylenecarbonate, γ-butyrolactone and methyl amyl ketone(2-heptanone). Among these examples, as a ketone solvent, methyl amylketone (2-heptanone) is preferable.

Examples of ester solvents include methyl acetate, butyl acetate, ethylacetate, isopropyl acetate, amyl acetate, isoamyl acetate, ethylmethoxyacetate, ethyl ethoxyacetate, propylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, ethylene glycolmonopropyl ether acetate, ethylene glycol monobutyl ether acetate,ethylene glycol monophenyl ether acetate, diethylene glycol monomethylether acetate, diethylene glycol monopropyl ether acetate, diethyleneglycol monoethyl ether acetate, diethylene glycol monophenyl etheracetate, diethylene glycol monobutyl ether acetate, diethylene glycolmonoethyl ether acetate, 2-methoxybutyl acetate, 3-methoxybutyl acetate,4-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate,3-ethyl-3-methoxybutyl acetate, propylene glycol monomethyl etheracetate, propylene glycol monoethyl ether acetate, propylene glycolmonopropyl ether acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl acetate,4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentylacetate, 4-methoxypentyl acetate, 2-methyl-3-methoxypentyl acetate,3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate,4-methyl-4-methoxypentyl acetate, propylene glycol diacetate, methylformate, ethyl formate, butyl formate, propyl formate, ethyl lactate,butyl lactate, propyl lactate, ethyl carbonate, propyl carbonate, butylcarbonate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butylpyruvate, methyl acetoacetate, ethyl acetoacetate, methyl propionate,ethyl propionate, propyl propionate, isopropyl propionate, methyl2-hydroxypropionate, ethyl 2-hydroxypropionate,methyl-3-methoxypropionate, ethyl-3-methoxypropionate,ethyl-3-ethoxypropionate, and propyl-3-methoxypropionate. Among theseexamples, as an ester solvent, butyl acetate is preferable.

Examples of nitrile solvents include acetonitrile, propionitrile,valeronitrile, butyronitrile and the like.

As desired, the organic developing solution may have a conventionaladditive blended. Examples of the additive include surfactants. Thesurfactant is not particularly limited, and for example, an ionic ornon-ionic fluorine and/or silicon surfactant can be used.

As the surfactant, a non-ionic surfactant is preferable, and a non-ionicfluorine surfactant or a non-ionic silicon surfactant is morepreferable.

In a case where a surfactant is added, the amount thereof based on thetotal amount of the organic developing solution is generally 0.001% to5% by mass, preferably 0.005% to 2% by mass, and more preferably 0.01%to 0.5% by mass.

The developing treatment can be performed by a conventional developingmethod. Examples thereof include a method in which the substrate isimmersed in the developing solution for a predetermined time (a dipmethod), a method in which the developing solution is cast up on thesurface of the substrate by surface tension and maintained for apredetermined period (a puddle method), a method in which the developingsolution is sprayed onto the surface of the substrate (spray method),and a method in which the developing solution is continuously ejectedfrom a developing solution ejecting nozzle while scanning at a constantrate to apply the developing solution to the substrate while rotatingthe substrate at a constant rate (dynamic dispense method).

As the organic solvent contained in the rinse liquid used in the rinsetreatment after the developing treatment in a case of a solventdeveloping process, any of the above-described organic solventscontained in the organic developing solution can be used which hardlydissolves the resist pattern. In general, at least one solvent selectedfrom the group consisting of hydrocarbon solvents, ketone solvents,ester solvents, alcohol solvents, amide solvents and ether solvents isused. Among these, at least one solvent selected from the groupconsisting of hydrocarbon solvents, ketone solvents, ester solvents,alcohol solvents and amide solvents is preferable, more preferably atleast one solvent selected from the group consisting of alcohol solventsand ester solvents, and an alcohol solvent is particularly preferable.

The alcohol solvent used for the rinse liquid is preferably a monohydricalcohol of 6 to 8 carbon atoms, and the monohydric alcohol may belinear, branched or cyclic. Specific examples thereof include 1-hexanol,1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol, 3-hexanol,3-heptanol, 3-octanol, 4-octanol, and benzyl alcohol. Among these,1-hexanol, 2-heptanol and 2-hexanol are preferable, and 1-hexanol and2-hexanol are more preferable.

As the organic solvent, one kind of solvent may be used alone, or two ormore kinds of solvents may be used in combination. Further, an organicsolvent other than the above-described examples or water may be mixedtogether. However, in consideration of the development characteristics,the amount of water in the rinse liquid, based on the total amount ofthe rinse liquid is preferably 30% by mass or less, more preferably 10%by mass or less, still more preferably 5% by mass or less, and mostpreferably 3% by mass or less.

As desired, the rinse solution may have a conventional additive blended.Examples of the additive include surfactants. Examples of the additiveinclude surfactants. As the surfactant, the same surfactants as thosedescribed above can be exemplified, a non-ionic surfactant ispreferable, and a non-ionic fluorine surfactant or a non-ionic siliconsurfactant is more preferable.

In a case where a surfactant is added, the amount thereof based on thetotal amount of the rinse liquid is generally 0.001% to 5% by mass,preferably 0.005% to 2% by mass, and more preferably 0.01% to 0.5% bymass.

The rinse treatment using a rinse liquid (washing treatment) can beconducted by a conventional rinse method. Examples of the rinse methodinclude a method in which the rinse liquid is continuously applied tothe substrate while rotating it at a constant rate (rotational coatingmethod), a method in which the substrate is immersed in the rinse liquidfor a predetermined time (dip method), and a method in which the rinseliquid is sprayed onto the surface of the substrate (spray method).

In the method of forming a resist pattern according to the presentembodiment which has been described above, since the resist compositionaccording to the first embodiment has been used, the sensitivity can beimproved during the formation of the resist pattern. In addition,according to the method of forming a resist pattern, lithographycharacteristics (the resolution, the roughness reduction, and the like)are further improved and the resolution is increased so that a resistpattern having an excellent shape can be formed.

EXAMPLES

Hereinafter, the present invention will be described in detail based onthe following examples, but the present invention is not limited tothese examples.

Synthesis Examples 1 to 14: Synthesis of Polymers P1 to P14

Polymers P1 to P14 were synthesized using compounds listed in Table 1according to a known method based on the molar ratios listed in Table 1.

With respect to the obtained polymers P1-P14, the copolymerizationcompositional ratio (the ratio (molar ratio) of each constitutional unitin the polymer compound) of each polymer compound acquired by ¹³C-NMR,and the weight average molecular weight (Mw) in terms of standardpolystyrene acquired by GPC measurement, and the molecular weightdispersity (Mw/Mn) thereof are listed in Table 1.

TABLE 1 Compositional ratio Constitutional unit Constitutional unitConstitutional unit (a10) (a0-1) (a0-2) Proportion Proportion Proportion(% by (% by (% by Molecular Polymer Type mole) Type mole) Type mole)weight Dispersity P1 (a101) 50 (m011) 30 (m021) 20 8100 1.7 P2 (a101) 50(m012) 30 (m021) 20 7700 1.7 P3 (a101) 50 (m013) 30 (m021) 20 7600 1.8P4 (a101) 50 (m011) 30 (m022) 20 8000 1.7 P5 (a101) 50 (m011) 45 (m021) 5 8000 1.6 P6 (a101) 50 (m011) 10 (m021) 40 7600 1.7 P7 (a101) 50(m011) 50 — — 8100 1.6 P8 (a101) 50 — 50 (m021) — 7700 1.6 P9 (a101) 50(m012) 50 — — 7900 1.7 P10 (a101) 50 (m013) 50 — — 7800 1.7 P11 (a101)50 — 50 (m022) — 7700 1.8 P12 (a101) 50 (m011) 30 (m023) 20 8200 1.8 P13(a101) 50 (m011) 30 (m024) 20 7900 1.7 P14 (a101) 50 (m014) 30 (m021) 208000 1.8

<Preparation of Resist Composition>

Respective components listed in Table 2 were mixed so as to bedissolved, thereby preparing resist compositions of each example.

TABLE 2 Compo- Compo- Compo- nent nent nent (A) (B) (D) Component (S)Example 1 (A) - 1 (B) - 1 (D) - 1 (S) - 1 (S) - 2 [100] [16] [4.2][3890] [2594] Example 2 (A) - 2 (B) - 1 (D) - 1 (S) - 1 (S) - 2 [100][16] [4.2] [3890] [2594] Example 3 (A) - 3 (B) - 1 (D) - 1 (S) - 1 (S) -2 [100] [16] [4.2] [3890] [2594] Example 4 (A) - 4 (B) - 1 (D) - 1 (S) -1 (S) - 2 [100] [16] [4.2] [3890] [2594] Example 5 (A) - 5 (B) - 1 (D) -1 (S) - 1 (S) - 2 [100] [16] [4.2] [3890] [2594] Example 6 (A) - 6 (B) -1 (D) - 1 (S) - 1 (S) - 2 [100] [116]  [4.2] [3890] [2594] Comparative(A) - 7 (B) - 1 (D) - 1 (S) - 1 (S) - 2 Example 1 [100] [16] [4.2][3890] [2594] Comparative (A) - 8 (B) - 1 (D) - 1 (S) - 1 (S) - 2Example 2 [100] [16] [4.2] [3890] [2594] Comparative (A) - 9 (B) - 1(D) - 1 (S) - 1 (S) - 2 Example 3 [100] [116]  [4.2] [3890] [2594]Comparative (A) - 10 (B) - 1 (D) - 1 (S) - 1 (S) - 2 Example 4 [100][161]  [4.2] [3890] [2594] Comparative (A) - 11 (B) - 1 (D) - 1 (S) - 1(S) - 2 Example 5 [100] [161]  [4.2] [3890] [2594] Comparative (A) - 12(B) - 1 (D) - 1 (S) - 1 (S) - 2 Example 6 [100] [16] [4.2] [3890] [2594]Comparative (A) - 13 (B) - 1 (D) - 1 (S) - 1 (S) - 2 Example 7 [100][16] [4.2] [3890] [2594] Comparative (A) - 14 (B) - 1 (D) - 1 (S) - 1(S) - 2 Example 8 [100] [16] [4.2] [3890] [2594]

In Table 2, each abbreviation has the following meaning. The numericalvalues in the parentheses are blending amounts (parts by mass).

(A)-1 to (A)-14: polymers P1 to P14 described above

(B)-1: acid generator represented by Chemical Formula (B)-1

(D)-1: acid diffusion control agent represented by Chemical Formula(D)-1

(S)-1: PGMEA

(S)-2: PGME

<Evaluation of Resist Composition>

A resist pattern was formed using each of the obtained resistcompositions, and the sensitivity (Eop), the resolution, and LWR wererespectively evaluated in the following manners.

[Formation of Resist Pattern]

An 8-inch silicon substrate to which a hexamethyldisilazane (HMDS) hadbeen applied was coated with the resist composition of each exampleusing a spinner, and a prebake (PAB) treatment was performed thereon ona hot plate at a temperature of 110° C. for 60 seconds so that thecomposition was dried to form a resist film having a film thickness of50 nm. Next, drawing (exposing) was performed on the resist film at anaccelerating voltage of 100 kV such that the target size was set to aline width of 32 mm and 1:1 line and space pattern (hereinafter,referred to as an “LS pattern”) using an electron beam lithographydevice JEOL-JBX-9300FS (manufactured by JEOL Ltd.), and a post exposurebake (PEB) treatment was performed thereon at 110° C. for 60 seconds.Subsequently, alkali development was performed at 23° C. for 60 secondsusing a 2.38 mass % tetramethylammonium hydroxide (TMAH) aqueoussolution “NMD-3” (trade name, manufactured by TOKYO OHKA KOGYO CO.,LTD.), and water rinsing was performed for 60 seconds using pure water.As the result, a 1:1 LS pattern with a line width of 32 nm was formed.

[Evaluation of Optimum Exposure Amount (Eop)]

An optimum exposure amount Eop (μC/cm²) at which the LS pattern with atarget size was formed according to the method of forming a resistpattern was acquired. The results are listed in Table 3.

[Evaluation of Resolution]

The limit resolution in the Eop, specifically, the minimum dimension ofa pattern to be resolved without collapsing while the exposure amountfrom the optimum exposure amount Eop was increased to form an LS patternwas acquired using a scanning electron microscope S-9380 (manufacturedby Hitachi High-Technologies Corporation). The results are listed inTable 3.

Using the LS pattern formed in the section of the “formation of resistpattern”, the 3σ which is the scale that indicates the LWR was acquired.The “3σ” indicates three times (3σ) (unit: nm) the standard deviation(σ) acquired based on the result of measurement performed by measuring400 sites of line positions in the longitudinal direction of the lineusing a scanning electron microscope (trade name: S-9380, manufacturedby Hitachi High-Technologies Corporation, accelerating voltage of 800V). In a case where the value of the 3σ is small, this indicates thatthe roughness of a line side wall is small and an LS pattern with auniform width is obtained.

TABLE 3 Eop Resolution LWR (mJ/cm²) (nm) (nm) Example 1 112 28 4.7Example 2 108 28 4.6 Example 3 115 29 4.8 Example 4 110 28 4.8 Example 5118 29 5.0 Example 6 108 29 5.1 Comparative 120 30 5.3 Example 1Comparative 104 31 5.7 Example 2 Comparative 114 30 5.3 Example 3Comparative 126 32 5.5 Example 4 Comparative 109 32 5.6 Example 5Comparative 122 31 5.4 Example 6 Comparative 122 32 5.9 Example 7Comparative 117 32 5.8 Example 8

Based on the results listed in Table 3, it was confirmed that the resistcompositions of Examples 1 to 6 to which the present invention had beenapplied had well-balanced sensitivity, resolution, and LWR, and theresolution and LWR were improved.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A resist composition which generates an acid uponexposure and whose solubility in a developing solution is changed due toan action of the acid, the resist composition comprising: a resincomponent (A1) whose solubility in a developing solution is changed dueto the action of the acid, wherein the resin component (A1) has aconstitutional unit (a0-1) derived from a compound represented byFormula (a0-1) and a constitutional unit (a0-2) derived from a compoundrepresented by Formula (a0-2):

wherein W represents a polymerizable group-containing group, and Ra⁰¹represents an acid dissociable group represented by Formula (a01-r-1) or(a01-r-2):

wherein Ra⁰¹¹ to Ra⁰¹³ each independently represents a linear orbranched aliphatic hydrocarbon group, Ra⁰¹⁴ represents a linear orbranched aliphatic hydrocarbon group, Ra⁰¹⁵ represents a group thatforms a monocyclic aliphatic cyclic group together with a carbon atom towhich Ra⁰¹⁴ is bonded, and the symbol “*” represents a bonding site;

wherein W represents a polymerizable group-containing group, and Ra⁰²represents an acid dissociable group represented by Formula (a02-r-1):

wherein Ra⁰²¹ and Ra⁰²² each independently represents a linear orbranched aliphatic hydrocarbon group, Ra⁰²³ represents an aromatichydrocarbon group which may have a substituent, and the symbol “*”represents a bonding site.
 2. The resist composition according to claim1, wherein the resin component (A1) further comprises a constitutionalunit (a10) represented by Formula (a10-1):

wherein R represents a hydrogen atom, an alkyl group having 1 to 5carbon atoms, or a halogenated alkyl group having 1 to 5 carbon atoms,Ya^(x1) represents a single bond or a divalent linking group, Wa^(x1)represents an (n_(ax1)+1)-valent aromatic hydrocarbon group, and n_(ax1)represents an integer of 1 or greater.
 3. A method of forming a resistpattern, comprising: forming a resist film on a support using the resistcomposition according to claim 1; exposing the resist film; anddeveloping the exposed resist film to form a resist pattern.
 4. Themethod of forming a resist pattern according to claim 3, whereinexposing the resist film comprises exposing the resist film to extremeultraviolet rays (EUV) or electron beams (EB).